62 Prof. Asa Gray on Sequoia and its History. 



two are merely of the same genus, or not quite that, but of a 

 single or very few species in each country, — when the point 

 which interests us is that this peculiar limited type should 

 occur in two antipodal places, and nowhere else. 



It would be tedious and, except to botanists, abstruse to 

 enumerate instances ; yet the whole strength of the case depends 

 upon the number of such instances. I propose, therefore, if 

 the Association does me the honour to print this discourse, to 

 append in a note a list of the more remarkable ones. But I 

 would here mention two or three cases as specimens. 



Our Rhus toxicodendron, or poison-ivy, is very exactly re- 

 peated in Japan, but is found in no other part of the world, 

 although a species much like it abounds in California. Our 

 other poisonous i^Aws {R. venenata), commonly called poison dog- 

 wood, is in no way represented in Western America, but has 

 so close an analogue in Japan that the two were taken for 

 the same by Thunberg and Linnseus, who called them R. 

 vernix. 



Our northern fox-grape ( Vttis lahrusca) is wholly confined 

 to the Atlantic States, except that it reappears in Japan and 

 that region. 



The original Wistaria is a woody leguminous climber with 

 showy blossoms, native to the Middle Atlantic States ; the 

 other species, which we so much prize in cultivation, W. si- 

 nensis, is from China, as its name denotes, or perhaps only from 

 Japan, where it is certainly indigenous. 



Our yellow wood ( Cladrastis) inhabits a very limited dis- 

 trict on the western slope of the AUeghanies. Its only and 

 very near relative {Maackia) is in Mandchuria. 



The Hydrangeas have some species in our Alleghany region. 

 All the rest belong to the Chino-Japanese region and its con- 

 tinuation westward. The same may be said of Philadelplius, 

 except that there are one or two mostly very similar in Cali- 

 fornia and Oregon. 



Our blue cohosh ( Caulopliyllum) is confined to the woods of 

 the Atlantic States, but has lately been discovered in Japan. 

 A peculiar relative of it, Diphylleia, confined to the higher 

 AUeghanies, is also repeated in Japan, with a slight difference, 

 so that it may barely be distinguished as another species. 

 Another relative is our twin leaf, Jejfersonia, of the Alleghany 

 region alone. A second species has lately turned up in Mand- 

 churia. A relative of this is Podophyllum, our mandrake, a 

 common inhabitant of the Atlantic United States, but found 

 nowhere else. There is one other species of it ; and that is in 

 the Himalayas. Here are four most peculiar genera of one 

 family, each of a single species in the Atlantic United States, 



