PALAEOBOTANY . In the See also:

• PRESENT

This second method of fossilization is termed petrifaction. In the See also:

• CASE
• CASE, JOHN (d. 1600)

Mistakes have often arisen from confusing these medullary casts with those of the stem as a whole. Although some See also:

• INFORMATION (from Lat. informare, to give shape or form to, to represent, describe)

Owing to this, it has become the common practice of palaeobotanists to give distinct generic names to detached parts of plants which may even have belonged to one and the same species. Thus the roots of Sigillaria are called Stigmaria, detached leaves Sigillariophyllunz, and the fructifications Sigillariostrobus; the name Sigillaria applies to the stem, which, however, when old and partly decorticated has been called Syringodendron, while its woody See also:

• CYLINDER (Gr. KvAwSpos, from KvXivaety, to roll)

The Glossopteris flora of See also:

• INDIA
• INDIA, FRENCH

Some of the better-attested examples, among which are a few of considerable interest, may now be considered. Of Cyanophyceae, as we should expect, the Palaeozoic remains ,are very doubtful. Gloioconis, found by Renault in a coprolite of Permian age, was regarded by him as a Cyanophycean allied to Gloeocapsa ; this may be so, but the See also:

• ARGUMENT

The boghead of See also:

• SCOTLAND
• SCOTLAND, CHURCH OF
• SCOTLAND, EPISCOPAL CHURCH OF

Radially placed gaps in the tissue (at first erroneously interpreted as medullary rays, but subsequently more aptly compared to the See also:

• AIR (from an Indo-European root meaning " breathe," " blow ")
• AIR, or ASBEN

- Later writers, influenced by the occasional occurrence of transverse walls in the smaller hyphae, have laid more stress on Laminariaceous affinities. The existence of these gigantic Algae in Palaeozoic times, attested by such well-preserved specimens, is a fact of great interest, though their systematic position is still' an open question: Pachytheca, a spherical organism, usually about the size of a small See also:

• PEA (Pisum)

In examining the tissues of fossil plants of that epoch nothing is more common than to meet with mycelial hyphae in Pangl and among the cells; in many cases the hyphae are septate, showing that the higher Fungi (Mycomycetes), as distinguished from the more algoid Phycomycetes, already existed. An endophytic Fungus referred to the latter group (Peronosporites antiquarius, W. See also:

• SMITH
• SMITH, ADAM (1723–1790)
• SMITH, ALEXANDER (183o-1867)
• SMITH, ANDREW JACKSON (1815-1897)
• SMITH, CHARLES EMORY (1842–1908)
• SMITH, CHARLES FERGUSON (1807–1862)
• SMITH, CHARLOTTE (1749-1806)
• SMITH, COLVIN (1795—1875)
• SMITH, EDMUND KIRBY (1824-1893)
• SMITH, G
• SMITH, GEORGE (1789-1846)
• SMITH, GEORGE (184o-1876)
• SMITH, GEORGE ADAM (1856- )
• SMITH, GERRIT (1797–1874)
• SMITH, GOLDWIN (1823-191o)
• SMITH, HENRY BOYNTON (1815-1877)
• SMITH, HENRY JOHN STEPHEN (1826-1883)
• SMITH, HENRY PRESERVED (1847– )
• SMITH, JAMES (1775–1839)
• SMITH, JOHN (1579-1631)
• SMITH, JOHN RAPHAEL (1752–1812)
• SMITH, JOSEPH, JR
• SMITH, MORGAN LEWIS (1822–1874)
• SMITH, RICHARD BAIRD (1818-1861)
• SMITH, ROBERT (1689-1768)
• SMITH, SIR HENRY GEORGE WAKELYN
• SMITH, SIR THOMAS (1513-1577)
• SMITH, SIR WILLIAM (1813-1893)
• SMITH, SIR WILLIAM SIDNEY (1764-1840)
• SMITH, SYDNEY (1771-1845)
• SMITH, THOMAS SOUTHWOOD (1788-1861)
• SMITH, WILLIAM (1769-1839)
• SMITH, WILLIAM (c. 1730-1819)
• SMITH, WILLIAM (fl. 1596)
• SMITH, WILLIAM FARRAR (1824—1903)
• SMITH, WILLIAM HENRY (1808—1872)
• SMITH, WILLIAM HENRY (1825—1891)
• SMITH, WILLIAM ROBERTSON (1846-'894)

The few and incomplete data which we at present possess as to Palaeozoic Fungi do not as yet justify any inferences as to the evolution of these plants. The writer is not aware of any evidence for the occurrence of Palaeozoic See also:

• LICHENS

This important class of plants will be described at the beginning of the Spermophyta under the name Pteridospermeae. The arrangement 'which we shall adopt for the Palaeozoic Pteridophyta is therefore as follows: I. Equisetales. II. Sphenophyllales. We must See also:

• BEAR
• BEAR, BLACK
• BEAR, BROWN
• BEAR, GRIZZLY
• BEAR, ISABELLINE
• BEAR, WHITE

The Calamarieae, now known to have been the chief Palaeozoic representatives of the See also:

• HORSETAIL (Equisetum)

There is evidence that in some, at least, of the Calamarieae the leaves of each verticil were united at the See also:

• BASE

In many Calamites there is evidence that the aerial stem sprang from a See also:

• HORIZONTAL

In the old stems the primary cortex was replaced by periderm, giving rise to a thick See also:

• MASS (O.E. maesse; Fr. messe; Ger. Messe; Ital. messa; from eccl. Lat. missa)
• MASS, IN

A striking feature is the presence of large, radiating intercellular cavities in the cortex, suggesting an aquatic habit. The young roots show a See also:

• DOUBLE
• DOUBLE (from the Mid. Eng. duble, the form which gives the present pronunciation, through the Old Er. duble, from Lat. duplus, twice as much)

The spores are frequently found to be still united in tetrads. In some species, e.g. the British C. Binneyana, numerous specimens have been examined and only one kind of spore observed ; here, then, there is a strong pre- sumption that the species was homosporous. In other cases, how- ever, e.g. C. Casheana, Will., two kinds of spore occur, in different sporangia, but on the same strobilus and even on the same sporangiophore. The megaspores, of which there are many in the megasporangium, have a diameter about three times that of the microspores. The See also:

• ABORTION (from Lat. aboriri, to fail to be born, or perish)

Binneyana), some- times free (e.g. C. Ludwigi); in all cases their free extremities formed a See also:

• PROTECTION

3, A). This singular arrangement has suggested doubts as to the correctness of the current See also:

• INTERPRETATION (from Lat. interpretari, to expound, explain, inter pres, an agent, go-between, interpreter; inter, between, and the root pret-, possibly connected with that seen either in Greek 4 p4'ew, to speak, or irpa-rrecv, to do)

4 (Plate). 3 Equisetum type of strobilus. In certain cases the strobili of Palaeozoic Calamarieae appear to have had essentially the sane organization as in the recent genus, the axis bearing sporangiophores only, without intercalated bracts. It is remarkable that fructifications apparently of this kind have been found by Renault in close association with the most ancient of the Calamarieae—Archaeocalamites. In these strobili the peltate scales, like the vegetative leaves of the plant, are in superposed verticils; each appears to have borne four sporangia (fig. 3, B). Other cones, however, namely, those known as Pothocites, have also been attributed on See also:

• GOOD, JOHN MASON (1764-1827)

E. Weiss first showed, immediately below the verticils of bracts, the position thus being the See also:

• REVERSE

A comparison, formerly suggested, with the two forms of leaf in Batrachian Ranunculi has not proved to hold good; the idea of an aquatic habit is contradicted by the anatomical structure, and the hypo-thesis that the plants were of scandent growth is more probable. The species of Sphenophyllum have a graceful See also:

• APPEARANCE (from Lat. apparere, to appear)

There are no recent stems with a structure quite like that of Sphenophyllum; so far as the primary structure is concerned, the nearest approach is among the Psiloteae, with which other characters indicate some affinity; the base of the stem in Psilotum forms some secondary wood. The diarch roots of a Sphenophyllum have been described by Renault, who has also investigated the leaves; they were strongly constructed mechanically, and traversed by slender vascular bundles branching dichotomously. Fructification.—Williamson thoroughly worked out, in petrified specimens, the organization of a cone which he named Bowmanites Dawsoni; it was subsequently demonstrated by Zeiller that this fructification belonged to a Sphenophyllum; the cones of the well-known species S. cuneifolium having a practically identical structure. The type of fructification described by Williamson and now named Sphenophyllum Dawsoni consists of long cylindrical cones, in external habit not unlike those of some Calamarieae. The axis, I In S. speciosum the leaves in a whorl were of unequal size. which in structure resembles the vegetative stem in its primary condition, bears numerous verticils of bracts, those of each verticil being coherent in their lower part, so as to form a disc or cup, from the margin of which the free limbs of the bracts arise. The sporangia, which are about twice as numerous as the bracts, are seated singly on pedicels or sporangiophores springing from the upper surface of the bract-verticil, near its insertion on the axis (fig. 6). As a rule two sporangiophores belong to each bract. The sporangium is attached to the enlarged distal end of its pedicel, from which it hangs down, so as to suggest an anatropous ovule on its funiculus. Dehiscence appears to have taken place at the free end of the sporangium; the spores are numerous, and, so far as observed, of one kind only. Each sporangiophore is traversed throughout its length by a vascular bundle connected with that which supplies the subtending bract.

This form of fructification appears, from Zeiller's researches, to have been common to several species of Sphenophyllum, but others show i,nportant See also:

• DIFFERENCES, CALCULUS OF (Theory of Finite Differences)

Sp.b, Section through sporangia- sm, Sporangia. phores. v.b. Vascular bundles. st, Laminae of sterile segments. cy, Stele of axis (Ax). In the longitudinal section the corresponding parts are shown. twelve in a whorl, are each composed of six segments, three being inferior or dorsal, and three See also:

• SUPERIOR

The great length and slender proportions of the segments give the cone a peculiar character, but the relations of position appear to leave no doubt as to the homologies with the fructification of Sphenophylleae; as regards the sporangiophores, Bowmanites Romeri occupies exactly the middle place between S. Dawsoni and Cheirostrobus. The axis of the cone in Cheirostrobus contains a polyarch stele, with solid wood, from the angles of which vascular bundles pass out, dividing in the cortex, to supply the various segments of the sporophylls. In the peduncle of the strobilus secondary tissues are formed. While the anatomy has a somewhat Lycopodiaceous character, the arrangement of the appendages is altogether that of the Sphenophylleae; at the same time Calamarian affinities are indicated by the characters of the sporangiophores and sporangia. The Sphenophyllales as a whole are best regarded as a synthetic group, combining certain characters of the Ferns and Lycopods with those of the Equisetales, while showing marked peculiarities of their own. Among existing plants their nearest affinities would appear to be with Psiloteae, as indicated not merely by the anatomy, but much more strongly by the way in which the sporangia are borne. There is good reason to believe that the ventral synangium of the Psiloteae corresponds to the ventral sporangiophore with its sporangia in the Sphenophyllales. Professor See also:

• THOMAS
• THOMAS (c. 1654-1720)
• THOMAS (d. 110o)
• THOMAS, ARTHUR GORING (1850-1892)
• THOMAS, CHARLES LOUIS AMBROISE (1811-1896)
• THOMAS, GEORGE (c. 1756-1802)
• THOMAS, GEORGE HENRY (1816-187o)
• THOMAS, ISAIAH (1749-1831)
• THOMAS, PIERRE (1634-1698)
• THOMAS, SIDNEY GILCHRIST (1850-1885)
• THOMAS, ST
• THOMAS, THEODORE (1835-1905)
• THOMAS, WILLIAM (d. 1554)

The leaves are highly compound, dividing dichotomously into several leaflets, each of which is deeply pinnatifid, with See also:

• FINE

Each leaf-See also:

• CUSHION (from O. Fr. coisson, coussin; according to the New English Dict., from Lat. coxa, a hip; others say from Lat. culcita, a quilt)

The primary wood of Lepidodendron forms a continuous cylinder, not broken up into distinct bundles; its development was clearly centripetal, the spiral elements forming more or less prominent peripheral groups. In the larger stems of most species there was a central pith, but in certain of the smaller branches, and throughout the stem in some species (L. rhodumnense, L. selaginoides), the wood was solid. A single leaf-trace, usually collateral in structure, passed out into each leaf. The primary structure of the stem was thus of a simple Lycopodiaceous type, resembling on a larger scale what we find in the upright stem of Selaginella spinosa. In most species (e.g. L. selaginoides, L. Wunschianum, L. Veltheimia.num) secondary growth in thickness took place, and secondary wood was added, (Scott, Studies.) P, Pith, almost destroyed. ph, Phloem and pericycle. x, Zone of primary wood. br, Stele of a branch. px, Protoxylem. yd, Periderm. x2, Secondary wood. l.b, Leaf-bases. The primary cortex between stele and periderm has perished.

(X41.1 in the centrifugal direction, showing -a regular radial arrangement, with medullary rays between the series of tracheides (fig. 9). The tissue thus formed often attained a considerable thickness. While S.C. (After Stur. Scott, Studies.) dodendron. s.c., Scar left by the leaf. v.b., Print of vascular bundle. p,p, Parichnos. 1, Ligule. a,a, Superficial prints below scar. primary phloem can be recognized with certainty in favourable cases. the question of the formation of secondary phloem by the cambium is not yet fully cleared up. In the Lepidodendron fullginosum of Williamson, shown by its leaf-bases to have been a Lepidophloios, the secondary wood is very irregular, and consists largely of parenchyma. The same is the case in Lepidodendron obovatum, one of the few species in which both external and internal characters are known.

The occurrence of secondary growth in these plants, demonstrated by Williamson's researches, is a point of great interest. Some See also:

• ANALOGY (Gr. avaXo-yLa, proportion)

The axis, which in anatomical structure resembles a vegetative twig, bears numerous spirally arranged sporophylls, each of which carries a single large sporangium on its upper surface (fig. Io). The sporophyll, usually almost horizontal in position, has an upturned lamina beyond the sporangium, and a shorter dorsal lobe, so that the form of the whole is somewhat peltate. A ligule is present immediately below the lamina, its position showing that the whole of the elongated horizontal h pedicel on which the spor- angium is seated corresponds to the short base of a FIG. lo.—Lepidostrobus. See also:

• DIAGRAM

In this fructification the organization is at first altogether that of a Lepidostrobus; in each megasporangium, however, only a single megaspore came to maturity, occupying almost the whole of the sporangial cavity (see fig. 12), but accompanied by the re-mains of its three abortive See also:

• SISTER

Each sporophyll bears a megasporangium, attached to its upper surface at the proximal end, containing a single large megaspore (fig. 13). The megasporangium is enclosed in an integument, which completely envelopes it, leaving only a narrow micropyle at the distal end (fig. 13). The long tentacles of the integument may have served to facilitate See also:

• POLLINATION

The roots, or at least their functional repre- sentatives, resembled those of Lepidodendron. The chief distinctive character of Sigillaria lies in the arrangement of the leaf-scars, which form conspicuous vertical series on the surface of the stem. bryo-See also:

• SAC

wp, Palisade layer of sporangium-wall. wi, Inner layer of wall. a, Base of sporangium. mg, Membrane of mega- spore or embryo-sac. In one great See also:

• DIVISION (from Lat. dividere, to break up into parts, separate)

Here also the distinction (After Weiss. Scott, Studies.) PQ has proved not to hold good, S. Brardi, for See also:

• FACE (from Lat. fades, derived either from facere, to make, or from a root fa-, meaning " appear "; cf. Gr. cbatvstv)

This See also:

• GAP

The See also:

• DISCOVERY

The morphology of Stigmaria has been much discussed; possibly the main axes, which do not agree perfectly either with rhizomes or roots, may best be regarded as comparable with the rhizophores of Selaginellae; they have also been compared with the embryonic stem, or protocorm, of certain species of See also:

• LYCOPODIUM

Filicales.--Of all Vascular Cryptogams the Ferns have best maintained their position down to the present day. Until recently it has been supposed that the class was well represented in the Palaeozoic period, and, indeed, that it was relatively, and perhaps absolutely far richer in species even than in the recent flora. Within the last few years, however, the position has completely changed, and the majority of the supposed Palaeozoic Ferns are now commonly regarded as more probably seed-bearing plants, a conclusion for which, in certain cases, there is already convincing evidence. The great majority of specimens of fossil fern-like plants are preserved in the form of carbonaceous impressions of fronds, often of remarkable perfection and beauty. The characters shown by such specimens, however, when, as is usually the case, they are in the barren state, are notoriously unstable, or of small taxonomic value, among recent .plants. Hence palaeobotanists have found it necessary to adopt a purely artificial system of See also:

• CLASSIFICATION (Lat. classis, a class, probably from the root cal-, cla-, as in Gr. icaMce, clamor)

These curious• appendages (Aphlebiae), at first regarded as parasitic growths, have been compared with the feathery outgrowths which occur on the rachis in the Cyatheaceous genus Hemitelia, and with the anomalous pinnules found in certain species of Gleichenia, at the points of bifurcation of the frond. Marattiaceae.—A considerable number of the Palaeozoic fern-like plants show indications—more or less decisive—of Marattiaceous affinities; some account of this group will first be given. The reference of these ferns to the family Marattiaceae, so restricted in the recent flora, rests, of course, primarily on evidence drawn from the fructifications. Typically Marattiaceous sori, consisting of exannulate sporangia united to form synangia, are frequent, and are almost always found on fronds with the character of Pecopteris, large, repeatedly pinnate leaves, resembling those of Cyatheaceae or some species of Nephrodium. In certain cases the anatomical structure of these leaves is known, and found to agree generally with that of recent coriaceous fern-fronds. The petiole was usually traversed by a single vascular bundle, hippocrepiform in section—a marked point of difference from the more complex petioles of recent Marattiaceae. There is evidence that in many cases these Pecopteroid fronds belonged to arborescent plants, the stems on which they were borne reaching a height of as much as 6o ft. These stems, known as Mega phylum when the leaves were in two rows, and as Caulopteris in the case of polystichous arrangement, are frequent, especially in the Permian of the See also:

• CONTINENT (from Lat. continere, "to hold together "; hence " connected," " continuous ")

The sori, or synangia, ranged in two series on the under-side of the fertile pinnules, are circular, each consisting of 3 to 6 sporangia, attached to a central receptacle and partly united to each other (fig. 15, A) ; the sporangia separated when mature, dehiscing by a ventral slit. Stur's genus Hawlea (fig. 15, H), characterized by the separation of the sporangia, may only re-present an advanced See also:

• STAGE (Fr. 6/age; from Lat. stare, to stand)

In a certain number of genera the reference to Marattiaceae is much more doubtful. In Dactylotheca, for example (fig. 15, C), a Pecopteroid (After various authors. Scott, Studies. Flo. 15.—Group of Palaeozoic fructifications of Ferns or Pteridosperms. A, Asterotheca. i, Pinnule bearing 8 synangia. 2, Synangium in side view. 3, In section, magnified. B, Renaultia. i, Fertile pinnule, nat. size. 2, Sporangium, enlarged. C, Dactylotheca, as in B.

D, Sturiella. Section of pinnule and synangium. a, Vascular bundle; c, hairs; b, d, annulus, magnified. E, Oligocarpia. Sorus in surface-view, magnified. F, Crossotheca. Fertile pinnule, bearing several tufts of micro-sporangia, magnified. G, Senftenbergia. Group of annulate sporangia, magnified. H, Hawlea. Synangium after dehiscence, magnified. J, Urnatopteris. I.

Part of fertile pinna, nat. size. 2, Sporangia, showing apical pores, magnified. Of the above, A, D, E, G and H, probably belong to true Ferns; F is the male fructification of a Pteridosperm (Lyginodendron) ; the See also:

• REST (O. Eng. rest, reste, bed, cognate with other Teutonic forms, e.g. Ger. Rast, Riiste, rest, and probably Gothic Rasta, league, i.e. resting or stopping place)

Certain fructifications have been referred to Gleicheniaceae (Oligocarpia, fig. 15, E), Schizaeaceae (Senftenbergia, fig. 15, G), Hymenophyllaceae and Osmundaceae, and on good grounds, so far as the external characters of the sporangia are concerned; our knowledge of most of the Ferns in question is, however, far too incomplete to justify us in asserting that they actually belonged to the families indicated. In the case of the Osmundaceae there is good evidence, from anatomical characters, for tracing the family back to the Palaeozoic; their oldest members sho v a distinct relationship to the Botryopterideae, de-scribed in the next See also:

• PARAGRAPH

The genus Zygopteris, of which numerous Carboniferous and Permian species are known, likewise had a monostelic stem, but the structure of its vascular cylinder was somewhat complex, resembling that of the most highly differentiated Hymenophyllaceae, with which some species of Zygopteris also agreed in the presence of axillary shoots. There is evidence that the stem in some species was a climbing one; the pinnate leaves, arranged on the stem in a two-fifths spiral, were dimorphic, the sterile fronds resembling some forms of (From a drawing by Mrs D. H. Scott. Scott, Studies.) Sphenopteris. The petioles have a somewhat complex structure, the bundle often having, in transverse section, the form of an H ; it has been proposed to subdivide the genus on the details of the petiolar structure. It is characteristic of Zygopteris and its near allies that two rows of pinnae were borne on each side of the rachis, at least in the fertile fronds. On the fertile rachis the sporangia were borne in tufts, much as in the preceding genus; they were still larger, reaching 2.5 mm. in length, and had a multiseriate annulus, extending, however, to both sides of the sporangium (see fig. 16, A and B). In Stauropteris, a genus showing some affinity with Zygopteris, the branched rachis of the fertile frond terminates in fine branchlets, each bearing a single, spherical sporangium, without any differentiated annulus (fig. 17). The spores in the sporangia have been found in a germinating condition; the stages of germination correspond closely with those observed in recent homosporous ferns (fig.

18). This fact strongly confirms the conclusion, drawn from morphological and anatomical characters, that the Botryopterideae were true Ferns. The genus Corynepteris of See also:

• BAILY, EDWARD HODGES (1788-1867)
• BAILY, FRANCIS (1774-1844)
• BAILY, WILLIAM HELLIER (1819-1888)

The simpler Ferns (Primofilices) of the period are for the most part referred to the remarkable family Botryopterideae, a group very distinct from —C D (From a drawing by Mr L. A. Boodle. Scott, Studies.) C, lying horizontally, an additional cell has been cut off between rhizoid and spore. (X 335.) any of the more modern families, though showing analogies with them in various directions. On the other hand there was the far more complex Marattiaceous type, strikingly similar in both vegetative and reproductive characters to the recent members of the family. Although doubts have lately been cast on the authenticity of Palaeozoic Marattiaceae owing to the difficulty in distinguishing between their fructifications and the pollen-bearing organs of Pteridosperms, the anatomical evidence (stem of Psaronius) strongly confirms the See also:

• OPINION (Lat. opinio, from opinari, to think)

We will begin with the Lyginodendreae, a group in which the anatomical characters indicated a systematic position between Ferns and Cycads, long before the reproductive organs were discovered. Lyginodendreae.—Of the genus Heterangium, which still stands very near the true Ferns, several species are known, the oldest L.t r (After Williamson. Scott, Studies.) x, Primary wood. hy, Hypoderma. x2, Secondary wood. l.t, l.t, Leaf-traces. p.c, Phloem and pericycle. r, Adventitious root. Several c, Cortex. leaf-bases are shown. being H. Grievii; of Williamson, from the Lower Carboniferous of Scotland. This plant had a long, somewhat slender, ridged stem, the ridges corresponding to the decurrent bases of the spirally arranged leaves (fig. 19). The specimens on which the genus was founded are petrified, showing structure rather than habit, but conclusive evidence has now been obtained that the foliage of H. Grievii was of the type of Sphenopteris (Diplotmema) elegans (fig.

20), and was thus in appearance altogether that of a Fern, with somewhat the habit of an Asplenium. The stem has a single stele, resembling in general primary structure that of one of the simpler species of Gleichenia; there is no pith, the wood extending to the centre of the stele. The leaf-traces, where they See also:

• TRAVERSE

Scott, Studies.) Part of frond. (3 nat. size.) as the secondary tissues increased, it had become superfluous for conducting purposes, and was adapted rather for water-storage. In the genus Lyginodendron, of which L. oldhamium, from the (Scott, Studies.) px, Protoxylem of strand. c.p, Conjunctive tissue. x, Centripetal. x2, Secondary wood. xi, Centrifugal primary wood. cb, Cambium. mx, Part of the internal wood. ph', Phloem. Coal Measures, is now the best-known of all Palaeozoic plants; the central wood has disappeared altogether and is replaced by pith ; the primary wood is only represented in the leaf-trace strands, which form a ring of distinct collateral bundles around the pith; (From a See also:

• MODEL (0. Fr. modelle, mod. modele; It. modello, pattern, mould; from Lat. modus, measure, standard)

Hdninghausi. Apart from the important advance shown in the anatomy of the stem, Lyginodendron agrees structurally with Heterangium. There is reason to believe that Lyginodendron oldhamium was a climbing plant comparable in some respects to such recent Ferns as Davallia aculeata. The roots were at first like those of Marattiaceae but grew in thickness like the roots of Gymnosperms. The first definite evidence of the mode of reproduction of Lyginodendron oldhamium was due to F. W. Oliver, who in 1903 identified the seed, Lagenostoma Lomaxii, by means of the glands on its cupule, which agree exactly with those on the associated leaves and stems of the plant (cf. figs. 24 and 25). No similar glands are known on any other Palaeozoic plant. Lagenostoma Lomaxii is a small See also:

• BARREL (a word of uncertain origin common to Romance languages; the Celtic forms, as in the Gaelic baraill, are derived from the English)

The seed was stalked, and there is an exact agreement in structure between the vascular strands of the stalk and cupule of the seed, and those of the rachis and leaflets of Lyginodendron, thus con-firming the evidence from the glands. The seed itself is of' a Cycadean type, and radially symmetrical. The single integument is united to the pucellus, except at the top, and is traversed by about nine vascular strands. In the See also:

• APEX

They are of the type known as Crossotheca, formerly regarded as a Marattiaceous fructification. The genus is characterized by the arrangement of the sporangia, which hang down from the lower surface of the little oval fertile leaflets, the whole resembling an epaulet with its fringe (fig. 15, F; fig. 28). In the case of Lyginodendron the Crossotheca occurs in connexion with the vegetative parts of the frond. Each fertile pinnule bore six, or rarely seven fusiform microsporangia, described as bilocularr not improbably each may represent a synangium The microspores are See also:

• TETRAHEDRAL

It is only quite at the close of the Palaeozoic period that Cycads begin to appear. The Lyginodendreae type of structure, how-ever, appears to have formed the transition not only to the Cycadales, but also to the extinct family Cordaiteae, the characteristic Palaeozoic Gymnosperms (see p. 107). Medulloseae.—In some respects the most rernarkable family of the Cycad-fern See also:

• ALLIANCE

Carboniferous species, such as M. stellata and M. Leuckarti, the arrangement is more complicated, the steles showing a differentiation into a central and a peripheral system ; the secondary growth was extensive and unequal, usually attaining its maxi-mum on the outer side of the peripheral steles. In certain cases the structure was further complicated by the appearance of extrafascicular zones exterior to the whole stelar system. The spirally arranged petioles (Myeloxylon) were of great size, and their decurrent bases clothed the surface of the stem; their (From a See also:

• SKETCH (directly adapted from Dutch schets, which was taken from Ital. schizzo, a rough draft, Lat. schedium, something hastily made, Gr. oxE&os, sudden, off-hand, axeb6v, near by; Ger. Skizze and Fr. esquisse are from the same source)

This plant may be regarded as anatomically the most primitive of the Medulloseae. In one member of the Medulloseae, there is direct evidence of reproduction by seeds, for in Neuropteris heterophylla Kidston has demonstrated that large seeds, of the size of' a See also:

• HAZEL (0. Eng. hresell; cf. Ger. Hasel, Swed. and Dan. Kassel, &c.,; Fr. noiselier, coudrier)

cc, Central column. apc, See also:

• APERTURE (from Lat. aperire, to open)

In A. fertilis, from the See also:

• POTTSVILLE

Scott, Studies.) boundary of the pith, as in the case in Lyginodendron. Stems (Mesoxylon) intermediate in structure between Poroxylon and Cordaites have lately been discovered in the English Coal Measures. Corresponding strands of primary xylem have been observed in stems of the genus Pitys (Witham), of Lower Carboniferous age, which consisted of large trees, probably closely allied to Cordaites. There appears, in fact, so far as stem-structure is concerned, to have been no sharp break between the typical Palaeozoic Gymnosperms and pronounced Pteridosperms such as Lyginodendron. The long, parallel-veined leaves of the Cordaiteae, which were commonly referred to Monocotyledons before their structure or connexion with other parts of the plant was known, have been shown by Renault to have essentially the same anatomy as a single leaflet of a Cycad such as Zamia. The vascular bundles, in particular, show precisely the characteristic collateral mesarch or See also:

• EXARCH (EEapxos, a chief person or leader)

30, founded on one of Grand' Eury's restorations, gives an idea of the habit of a tree of the genus Dorycordaites, characterized by its lanceolate acute leaves; in the typical Cordaites they were of a blunter shape, while in Poacordaites they were narrow and grass-like. The leaves as a rule far exceeded in size those of any of the Coniferae, attaining in some species a length of a See also:

• METRE ((terpuc?, sc. rFxvf, from Gr. Or poi', measure)

Some of the stamens are inserted between the bracts, in an apparently axillary position, while others are grouped about the apex of the axis. Each stamen consists of a long filament, bearing several erect, cylindrical pollen-sacs at its See also:

• SUMMIT

Grand' Euryi. Lower part of canal, enlarged; o, cavity of canal, surrounded by a sheath of cells, dilated towards the bottom of canal, in which a large pollen-See also:

• GRAIN (derived through the French from Lat. granum, seed, from an Aryan root meaning " to wear down," which also appears in the common Teutonic word " corn ")

Within the pollen-chamber, and in the canal, pollen-grains are found, agreeing with those in the anthers, but usually of larger size (fig. 32, C). It was in this case that Renault first made the exceedingly interesting discovery that each pollen-grain contains a group of cells, presumably representing an antheridium (fig. 32, C). Recent observations have completely confirmed Renault's interpretation of the facts, on which some doubt had been cast. In the isolated seeds of Cordaitales and Pteridosperms, pollen-grains are often found within the pollen-chamber, and the pluricellular structure of these pollen-grains has been repeatedly demonstrated. In the light of our present knowledge of Ginkgo and the Cycads, there can scarcely be a doubt that spermatozoids were formed in the cells of the antheridium of the Cordaitean pollen-grain and that of other Palaeozoic Spermophyta; the antheridium is much more developed than in any recent Gymnosperm, and it may be doubted whether any pollen-See also:

• TUBE (Lat. tuba)

Their internal structure is sometimes admirably preserved, so that the endosperm with its archegonia is clearly shown (fig. 32, D). It is a curious fact that in no case has an embryo been found in any of these seeds; probably fertilization took place after they were shed, and was followed immediately by germination. There is good evidence that many of the seeds belonged to Cordaitales, especially those seeds which had a flattened form, such as Cardiocar pus, Cycadinocarpus, Samaropsis, &c. Seeds of this kind have been found in connexion with the Cordaianthus inflorescences; the winged seeds of Samaropsis, borne on long pedicels, are attributed by Grand' Eury to the genus Dorycordaites. Many other forms of seed, and especially those which show radial symmetry, as for example Trigonocar pus, Stephanospermum and Lagenostoma belonged, as we have seen, to some of the plants grouped under Pteridospermeae, though other Pteridosperms had flattened seeds not as yet distinguishable from those of Cordaitales. The abundance and variety of Palaeozoic seeds, still so often of undetermined nature, indicate the vast extent of the spermophytic flora of that period. The modern Gymnospermous orders have but few authentic representatives in Palaeozoic rocks. The history of the See also:

• GINKGOALES

The male sporophylls are similar in form to the vegetative leaves, but smaller; sunk in their parenchyma are numerous tubular loculi, containing large pollen-grains, which are pluricellular like those of Cordaites; the female fructification had not yet been identified with certainty. The curious male sporophylls may perhaps be remotely comparable to those recently discovered in Mesozoic Cycadophyta, of the group Bennettiteae. Some leaves of Cycadean habit (e.g. Pterophyllum, Sphenozamites) occur in the Coal Measures and Permian, and it is possible that the obscure Coal Measure genus Noeggerathia may have Cycadean affinities. A fructification from the Permian of Autun, named Cycadospadix milleryensis by Renault, appears to belong to this family. Now that the numerous specimens of wood formerly referred to Coniferae are known to have belonged to distinct orders, but few true Palaeozoic Conifers remain to be considered. The most important are the upper Coal Measure or Permian genera Walchia, Ullmannia and Pagiophyllum, all of which resembled certain Araucarieae in habit. In the case of Walchia there is some evidence as to the fructifications, which in one species (W. fliciformis) appear to be comparable to female Araucarian cones. There are also some anatomical points of agreement with that family. It is probable, however, that under the same generic name very heterogeneous plants have been confounded. In the case of Ullmannia the anatomical structure of the leaf, investigated by Solms-Laubach, proves at any See also:

• RATE

The very remarkable plumose seeds described by Renault under the name Gnetopsis are of uncertain affinity, but have much in common with Lagenostoma, the seed of Lyginodendron. (All after Renault.) Succession of Floras. Our knowledge of vegetation older than the Carboniferous is still far too scanty for any satisfactory history of the Palaeozoic Floras to be even attempted; a few, however, of the facts may be advantageously tecapitulated in See also:

• CHRONOLOGICAL

Any detailed account of the horizons of Carboniferous plants would carry us much too far. For our present purpose we may See also:

• DIVIDE

The heterogeneous " Ferns " grouped under Spheno-pterideae are especially abundant. Ferns of the genera referred to Marattiaceae are common, but arborescent stems of the Psaronius type are still comparatively rare. Numerous fronds such as Alethopteris Neuropteris, Mariopteris, &c., belonged to Pteridosperms, of which specimens showing structure are frequent in certain beds. Cordaites, Dorycordaites and many stems of the Mesoxylon type represent Gymnosperms; the seeds of Pteridosperms and Cordaiteae begin to be common. The Upper Coal Measures (Stephanian) are characterized among the Calamarieae, now more than ever abundant, by the prevalence of the Calamodendreae; new species of Sphenophyllum make their appearance; among the Lycopods, Lepidodendron and its immediate allies diminish, and smooth-barked Sigillariae are the characteristic representatives. " Ferns " and Pteridosperms are even more strongly represented than before, and this is the age in which the supposed Marattiaceous tree-ferns reached their maximum development. Among Pteridosperms it is the family Medulloseae which is especially characteristic. Cordaiteae still increase, and Gymnospermous seeds become extraordinarily abundant. In the Upper Coal Measures the first Cycadophyta and Coniferae make their appearance. The Permian, so far at least as its lower beds are concerned, shows little See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

The sketch given above extends, for the later periods, to the vegetation of the See also:

• NORTHERN

The extraordinary abundance of Glossopteris in Permo-Carboniferous rocks of See also:

• AUSTRALIA

I.—Glossopteris frond, with portion enlarged to show the venation. their appearance, almost necessitates the conclusion that (Natural size =36 cm. in length.) From Lower Gondwana rocks of India. the change in the character of the vegetation was con- nected with a lowering of temperature and the prevalence of glacial conditions over a wide area in India and the southern hemisphere. There can be little doubt that the Indian Lower Gondwana rocks, in which the boulder-beds and the Glossopteris flora occur, must be ,regarded as belonging to a vast continental area of which remnants are preserved in Australia, South Africa and South America. This continental area has been described as " Gondwana Land," a See also:

• TRACT (from Lat. tractare, to treat of a matter, through Provencal tractat and Ital. trattato)

Permian vegetation of the north, but differs from it to such an extent as to constitute a distinct flora. We must begin by briefly considering this southern Palaeozoic See also:

• PROVINCE
• PROVINCE (Lat. provincia; perhaps a contraction of providentia)

The genus possessed small broadly oval or triangular leaves in addition to the large fronds like that shown in fig. 1; it was with the smaller leaves that Mr Arber discovered sporangia exhibiting certain points of resemblance to the micro-sporangia of modern Cycads. We cannot as yet say whether these bodies represent a somewhat unusual type of fern sporangium or whether they are microsporangia: if the latter supposition is correct the plant must have been heterosporous; but we are still without evidence on this point. Associated with Glossopteris occurs another fern, Gangamopteris, usually recognized by the absence of a well marked midrib, though this character does not always afford a satisfactory distinguishing feature. In view of recent discoveries which have demonstrated the Pteridosperm nature of many supposed ferns of Palaeozoic age, we must admit the possibility that the term fern as applied to Glossopteris and Gangamopteris may be incorrect. An Eq.uisetaceous plant; which Brongniart named Phyllotheca in 1828, is another member of the same flora; this type bears a close. resemblance to Equisetum in the long internodes and the whorled leaves encircling the nodes, but differs in the looser leaf-sheaths and in the long spreading $liform leaf-segments, as also in the structure of the cones. Phyllotheca has been recognized in Europe in strata of Palaeozoic age, and Professor Zeiller has discovered a new species—P. Ralliiin Upper Carboniferous rocks in Asia See also:

• MINOR
• MINOR (Lat. for smaller, lesser)
• MINOR, ROBERT CRANNELL (1839-1904)

A characteristic member of the southern botanical province, Schizoneura gondwanensis (fig. 2) of India, is represented also by a closely allied if not an identical species—S. paradoxa—in the Lower Trias (See also:

• BUNTER