Order 13.— CRUCIFERJ3. 227 



by a false partition, with parietal placentae. Fruit a siliquo, or silicle, usually 2- 

 celled. Stigmas 2, sessile. Seeds 2-rowed in each cell, but often so intercalated 

 as to form but one row. Embryo with tho 2 cotyledons variously folded on the 

 radicle. Albumen 0. 



Must. 256. 312, 3G5, 44T, 443. 



Genera 195, species 1600. This is a very natural order, larger than any of tho preceding. 

 The greater part of the species are found in the temperate zones. About 100 are peculiar to 

 this continent. 



Properties. The Crucifers as a class are of much importance to man. They furnish several 

 alimentary articles, which are very nutritious, as the Turnip, Cabbage, Cauliflower ; several 

 others are used as condiments, as Mustard, Iiadish, Cochlearia, etc. They all possess a peculiar 

 acrid, volatile principle, dispersed through every part, often accompanied by an elherial oil 

 abounding in sulphur. Tliey are also remarkable for containing more nitrogen than other vege- 

 tables, for" which reason ammonia is generally evolved in their putrefaction. In medicine they 

 are eminently stimulant and antiscorbutic. None are really poisonous, although very acrid. 

 The root of Isatis tinctoria affords a blue coloring matter. 



Ohs. The genera of this large order were arranged into sub-orders by De Candolle, according 

 to their various modes of folding the cotyledon upon tho radicle, which modes are as follows: 

 1. Cotyledons accumbent, the radicle turned round and applied to the edges of the cotyledons, 

 represented thus 0=. 2. Cotyledons incumbent, the radicle applied against the back of one of 

 the cotyledons, || . 3. Cotyledons conduplicate, radicle folded as iu the last case, but the coty- 

 ledons bent so as partly to enfold it, 0», as in the mustard. 



In the analysis of the Crucifers it is indispensable that the specimens be in fruit as well as 

 flower, and that the student bring to bear all bis patience and resolution in the study of the 

 above and other forms of structure in the seed, however minute. In the following synopsis the 

 student may use in analysis either the artificial arrangement of the Genera or the less obvious 

 but more natural arrangement of the 



TRIBES. 



{ SILIQUOSJ3, — fruit a silique opening by valves. (Tribes.) 



Tribe 1. Aeabide.e. Seeds flattened, often bordered ; cotyledons 0= General — 10 



Tribe 2. Sisimuef..e. Seeds oblong, not bordered ; cotyledons II Gen. 11 — 14 



Tribe 3. Br.ASSiCE.£. Seeds globular, cotyledons 0». Flowers yellow Gen. 15, 16 



$§ SILICULOSjE, — fruit a silicle opening by valves when more than 2-secded. (Tribes.) 



Tribe 4. Alyssine.e. Dissepiment broad. Cotyledors 0= Gen. IT — 21 



Tribe 5. Camrline.e. Dissepiment broad. Cotyledons II Gen. 22, 23 



Tribe 6. Thlaspe.e. Dissepiment narrow. Cotyledons = Gen. 24 



Tribe 7. Lepidine-j:. Dissepiment narrow. Cotyledons 0|| Gen. 25 — 27 



TribeS. Isatide.e. Dissepiment 0. Silicle 1-seeded, indehiscent Gen. 28 



5§§ LOMENTACE^E,— fruit a jointed silique, partitioned across. (Tribes.) 



Tribe 9. Cakalinejb. Cotyledons 0=, seeds compressed.. Gen. 29 



Tribe 10. R apu ANEiB. Cotyledons 0», seeds globous Gen. 30 



ARTIFICIAL KEY TO THE GENERA. 



§ Fruit a silique. Seeds in a double row Genera 1, % 



Seeds in a single row. Flowers cyanic (a). 

 Flowers xanthic (b) 



a Flowers purple, single. Stigma capitate. Plant native ; Genera 8 



O Flowers purple (or white and double). Stigmas horned. Cultivated Gen. 4, 14 



a Flowers white or roseate. Siliques flattened,— raised on a filiform stipe Gen. 13 



— sessile, having no stipe Gen. 5, 6, T 



b Seeds globular, with cotyledons conduplicate (0») Gen. 15. 16 



b Seeds oblong or lens-shaped. Siliques terete or flattened, veinless Gen. S, 9 



Siliques squarish, valves 1 — 3-veined Gen. 10, 11, 12 



§5 Fruit a silicle. Silicle turgid or flattened, with a broad partition (c). 

 Silicle flattened contrary to the narrow partition (d). 



Siliclo with no partition, 1-seeded. Flowers yellow Gen. 28 



C Ornamental exotics, variously colored. Gardens Gen. 17, 18 



C Native plants with— flowers cyanic, white Gen. 19, 20*28 



— flowers yellow. Silieles ? oblong Gen. 1 



Silicles ovoid or globular Gen. 21, 22 



d Seeds several in each cell. Silicle triangular Gen. 25 



d Seeds only 2, — one in each cell. The two outer petals larger Gen. 2J 



The petals all equal Gen. 26, 27 



f§§ Fruit a loment, jointed and partitioned across Gen. 29, 30 



