Geographical Distribution of the Crucijerce. 3 



Of this genus the species most frequently seen is the T. glabra, 

 common enough on the shores of Lake Superior and the banks of 

 the streams running into Hudson's Bay; it extends northward as 

 far as lat. 64°, and in the more northern latitudes is accompanied 

 by the T. patula, and T. retrofracta, which are distinguished 

 principally by their spreading and ret refract pods. Within the 

 arctic circle the T. mollis and T. diffusa are joined to them, 

 when the T. retrofracta drops off. The T. pa tula, although not 

 reported as higher than 6S Q on the continent, has nevertheless a 

 variety in Greenland, from which country Sir W. J. Hooker has 

 received it. The Turritis macrocarpa and T. striata are western 

 plants; the T. brachycarpa is confined to the Michigan territory. 



The genus Arabis has 15 species now discovered in North 

 America, of which five are natives of this province, the A.petroza, 

 hirsuta, lyrata, laevigata, and Canadensis. The A. hirsuta, fre- 

 quent near the coast of Hudson's Bay, extends to the Oregon, 

 and alono* the shores of the Pacific as far as Sitka. The 

 A. petrcaa is also marked by Ohamisso as a plant of Unal- 

 ashka. On the north shores of the St. Lawrence below Quebec, 

 the A. laevigata is common, and is met with here and there 

 throughout Canada. The two other Canadian species, the A. 

 lyrata and Canadensis, like the last, travel southwards, and are 

 seen scattered over the States as far as Virginia, Georgia, and the 

 Arkansas. Two species, which appear to be confined to Labrador, 

 the A. Alpina and A. striata, are amongst the cruciferse of Europe. 

 Of this rather extensive genus there are still 7 or 8 species to be 

 found in North America, but to the southward of the boundary 

 line. Four of these are the discovery of the indefatigable Xuttall 

 amongst the Rocky Mountains and towards the Oregon. 



The bitter cresses, or Cardamines, not so numerous in species 

 as the last genus, and more seldom met with in the north than the 

 genera, Turritis and Arabis have the leaves generally pinnately di- 

 vided, which is a form little observed in the other two. Carda- 

 mine rotundifolia, and C. bellidifolia, have undivided leaves, and 

 are extensively distributed, each in its chosen habitat. The former 

 best known in the eastern and northern states, was also procured 

 by Drummoud in the Rocky Mountain defiles, from lat. 52 Q to 

 57°, which for one season, the summer of 1S5G, he took as the 

 range for his botanical researches. Lake Superior and Hudson's 

 Bay have also been quoted as affording this plant. The C. bellidi- 

 folia is a native of Arctic America, but, like some other plants of 



