Online Encyclopedia

Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.

CRUCIFERAE

Online Encyclopedia
Originally appearing in Volume V07, Page 522 of the 1911 Encyclopedia Britannica.
» Make a correction to this article.
» Add information or comments to this article.
Spread the word: del.icio.us del.icio.us it!

CRUCIFERAE , or Crucifer See also:

family, a natural See also:order of flowering See also:plants, which derives its name from the cruciform arrangement of the four petals of the See also:flower. It is an order of herbaceous plants, many of which, such as wallflower, stock, See also:mustard, See also:cabbage, See also:radish and others, are well-known See also:garden or See also:field-plants. Many of the plants are annuals; among these are some of the commonest weeds of cultivation, shepherd's See also:purse (Capsella Bursa-pastoris), charlock (Brassica Sinapis), and such See also:common See also:Diagram (Brassica). Flower with Perianth removed. (After Baillon.) plants as hedge mustard (Sisymbrium officinale), See also:Jack-by-thehedge (S. Alliaria or Alliaria officinalis). Others are biennials producing a number of leaves on a very See also:short See also:stem in the first See also:year, and in the second sending up 'a flowering shoot at the expense of the nourishment stored in the thick tap-See also:root during the previous See also:season. Under cultivation this root becomes much enlarged, as in See also:turnip, swede and others. Wallflower (Cheiranthus Cheiri) (fig. I) is a perennial. The leaves when See also:borne on an elongated stem are arranged alternately and have no stipules. The See also:flowers are arranged in racemes without bracts; during the See also:life of the flower its stalk continues to grow so that the open flowers of an inflorescence stand on a level (that is, are corymbose).

The flowers are See also:

regular, with four See also:free sepals arranged in two pairs at right angles, four petals arranged See also:cross-See also:wise in one See also:series, and two sets of stamens, an See also:outer with two members and an inner with four, in two pairs placed in the See also:middle See also:line of the flower and at right angles to the outer series. The four inner stamens are longer than the two outer; and the stamens are hence collectively described .as tetradynamous. The See also:pistil, which is above the See also:rest of the members of the flower, consists of two carpels joined at their edges to See also:form the ovary, which becomes two-celled by subsequent ingrowth of a septum from these See also:united edges; a See also:row of ovules springs from each edge. The See also:fruit is a pod or siliqua splitting by two valves from FIG. 4.—Cruciferous Fruits. (After Baillon.) A, Cheiranthus Cheiri. D, Lunaria biennis, showing the septum B, Lepidium sativum. after the carpels have fallen away. C, Capsella Bursa-pastoris. E, Crambe maritima. below upwards and leaving the placentas with the seeds attached to the replum or framework of the septum. The seeds are filled with the large embryo, the two cotyledons of which are variously folded.

In germination the cotyledons come above ground and form the first See also:

green leaves of the plant. See also:Pollination is effected by aid of See also:insects. The petals are generally See also:white or yellow, more rarely See also:lilac or some other See also:colour, and between the bases of the stamens are See also:honey-glands. Some or all of the anthers become See also:twisted so that insects in probing for honey will See also:touch the anthers with one See also:side of their See also:head and the capitate stigma with the other. Owing, however, to the See also:close proximity of stigma and anthers, very slight irregularity in the movements of the visiting See also:insect will cause self-pollination, which may also occur by the drop- A ping of See also:pollen from the FIG. 5.—Seeds of Cruciferae cut anthers of the larger stamens across to show the radicle and on to the stigma. cotyledons. (After Baillon.) Cruciferae is a large order A, Cheiranthus Cheiri. containing nearly 200 genera B, Sisymbrium Alliaria. and about 1200 See also:species. It Figures 2-5 are from Strasburger's Lehrbuch has a See also:world-wide See also:distribution, der Botanik, by permission of Gustav See also:Fischer. but finds its See also:chief development in the temperate and frigid zones, especially of the See also:northern hemisphere, and as Alpine plants. In the subdivision of the order into tribes use is made of See also:differences in the form of the fruit and the manner of folding of the embryo. When the fruit is several times longer than broad it is known as a siliqua, as in stock or wallflower; when about as See also:long as broad, a silicula, as in shepherd's purse.

A C D The order is well represented' in Britain—among others by See also:

Nasturtium (N. officinale, See also:water-See also:cress), Arabis (See also:rock-cress), Cardamine (See also:bitter-cress), Sisymbrium (hedge mustard, &c.; S. Trio is See also:London See also:rocket, so-called because it sprang up after the See also:fire of 1666), Brassica (cabbage and mustard), Diplotaxis (rocket), Cochlearia (See also:scurvy-grass), Capsella (shepherd's purse), Lepidium (cress), Thlaspi (See also:penny-cress), Cakile (See also:sea rocket), Raphanus (radish), and others. Of economic importance are species of Brassica, including mustard (B. See also:nigra), white mustard, used when See also:young in salads (B. See also:alba), cabbage (q.v.) and its numerous forms derived from B. oleracea, turnip (B. campestris), and swede (B. Napus), Raphanus sativus (radish), Cochlearia Armor a c i a (See also:horse-radish), Nasturtium officinale (water - cress),. showing Flower and Fruit. Reduced. Lepidium sativum (garden cress). Isatis affords a See also:blue dye, See also:woad. Many of the genera are known as ornamental garden plants; such are Cheiranthus (wallflower), Matthiola (stock), Iberis (candy-tuft), Alyssum (See also:Alison), Hesperis (See also:dame's See also:violet), Lunaria (honesty) (fig. 6), Aubrietia and others.

End of Article: CRUCIFERAE

Additional information and Comments

There are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML.
Site content, images, and layout Copyright © 2006 - Net Industries, worldwide.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.

Links to articles and home page are always encouraged.

[back]
CRUCIAL (from Lat. crux, a cross) 		[next]
CRUDEN

Site © 2006 - Net Industries