CRUCIFEROUS TRIBE. 37 



attributed their unpleasant odour when rotting. Some 

 contain a large portion of sulphur. Oil is contained in 

 the seeds of many, in such quantities as to be a valu- 

 able article of commerce. There are about 800 species, 

 one-eighth of which only are found in America ; the 

 remainder, for the most part, inhabit the cold and tem- 

 perate regions of Europe and Asia. Upwards of 200 

 grow in the frigid zone, where they form a large pro- 

 portion of the vegetation. 



This Order contains all the plants which were placed 

 by Linnaeus in the Class Tetradynamia ; that is, all such 

 as are distinguished by having 6 stamens, 4 long and 

 2 short. Modern botanists found the main distinctions 

 of the genera on the position of the radicle or embryo 

 root with relation to the cotyledons, or seed-lobes ; but 

 as this arrangement presents difficulties to the young 

 student in botany, it is not considered advisable to adopt 

 it here. 



* Seed-vessel^ a pouch (silicle) or short pod. 

 t Pouch 2-valved, with a central vertical partition. 



1. THLASPI (Penny Cress). Pouch rounded, flat, 

 notched ; valves boat-shaped, winged at the back ; seeds 

 numerous. (Name from the Greek, thlao, to flatten.) 



2. CAPSELLA (Shepherd's Purse). Pouch inversely 

 heart-shaped, flat ; valves boat-shaped, keeled, but not 

 winged ; seeds numerous. (Name, a little capsa, or 

 seed-case.) 



3. HUTCHINSIA. Pouch elliptical, entire ; valves boat- 

 shaped, keeled, not winged ; cells 2-seeded. (Named in 

 honour of Miss Hutchins, of Bantry, Ireland, an emi- 

 nent botanist.) 



4. TEESDALIA. Pouch roundish, notched; valves 

 boat-shaped, keeled ; cells 2-seeded ; stamens having ^ a 

 little scale at the base of each, within. (Named in 

 honour of Mr. Teesdale, a Yorkshire botanist.) 



5. LEPIDIUM (Pepper-wort). Pouch roundish ; valves 



