2 Geographical Distribution of the Cruciferce. 



placentae, their margination, and the position of the cotyledon with- 

 in the seed. The greater portion of these nine tribes have their 

 •ies generally diffused, some on the western side of the Rocky 

 Mountains, others on the eastern plateau, and the Atlantic board. 

 The tribe Isatidese is an exception, however, as it appears only in 

 the far west, where six or seven species of Thysajiocarpi occur. 



Commencing with the Arabideji, the first tribe of the erei 

 siliquose division, we have three species of Oheiranthus in 

 North America. The 0. capitatus in California and Oregon, 

 passing into British territory from Paget Sound, the C. Pallasii 

 on the North West coast, and the C. Hesperidoidcs, in Pensyl- 

 vania, Kentucky, Illinois and Arkansas. No locality in the British 

 territories eastward of the Mountain, appears to be quoted by any 

 author for American Wallflowers; and certainly I have not heard 

 of them native in Canada. The fragrant and most grateful, the 

 Oheiranthus cheiri, is only to be found in our gardens. 



The Nasturtiums (Water -cresses) are well sprinkled over 

 the country south of Canada, but more rarely elsewhere. We 

 possess the N. palustre, however, in all quarters, wherever the 

 ground is suitable for it, throughout the length and breadth of 

 the land. The N. natans, a scarcer plant, is to be found in 

 Canada and the United States, along the borders of small Takes, 

 and may be distinguished by its immersed leaves being many- 

 parted with capillary segments. The other Nasturtiums are dis- 

 tributed to the number of five in the United States, and of four 

 in the Oregon and on the north west coast. 



Barbarea prcecox attains to a high latitude, say 6S°, and 

 we have it also along the banks of rivers in Canada. The Bar- 

 barea vulgaris, common in the Northern States, is also found in 

 Oregon and on the north-west coast, running north to Sitka, 

 within the Russian territories. There may be difference of opinion, 

 whether this be an introduced plant or not, according to the quar- 

 ter where it may be found. Occurring in settled districts in the 

 States, one might piononnce it introduce,!, while in new or wilder 

 situations another would at once sav it was indigenous. It is the 

 Yellow Rocket and Winter Cress of the English ; the Cresse de 

 Terre of the French ; and Ilierba de Santa Barbara of the 

 Spanish. 



Passing over the genus Strcptanthus, of which three species 

 occur in the United States, three in the rocky mountains, anl six 

 in California and Oregon, we arrive at the Turritis of Dillenius. 



