192 Prof. Gray on the Botany of Japan, 
Photonia Leptandra Sporobolus 
Astilbe Callicarpa Arundinaria 
Mitella © Cedronella Adiantum 
Hydrangea Amsonia Onoclea 
Ltea 
Here are about 90 extra-Huropean genera or forms, 64 of 
which are absent from Western North America out of the trop- 
ies (the latter comprising a very large part of the most striking 
representative species), and almost as many more are divided 
between North America and extra-tropical (chiefly Northern and 
Eastern) Asia. About 40 of the latter are genera or groups of 
single, or else of two or few closely related species, peculiar, or 
nearly peculiar, to the regions just mentioned. 
This list should be supplemented by those additional North 
American genera which have one or more closely representative 
species in the Himalayan region only, such as Podophyllum, Py- 
rularia, &c.; and also by the numerous cases in which Eastern 
American plants are represented in the Himalayo-Japanese 
region by strikingly cognate, although not congeneric species; 
such as our Macrotys by Pityrosperma; Schizandra by Kadsura 
and Spherostema ; Neviusia by Kerria and Rhodotypus ; Calycan- 
thus by Chimonanthus; Cornus florida by Benthamia ; Prosariés 
(vol. xxii, second series) ; where I had noticed the facts,—1. that 
a large percentage of our extra-European types are shared w! 
Eastern Asia; and 2, that no small part of these are unknown 
in Western North America. But Mtr Bentham was first to 
state the natural conclusion from all these data,—though I know 
not if he has even yet published the remark,—viz., that the 1° 
terchange between the temperate floras even of the western part 
of the Old World and of the New has mainly taken place 1 
Asia. Notwithstanding the few cases which point in the oppo 
site direction (e. g. Hriocaulon septanguiare, Seats: Subularia, 
tula alba), the general statement will be seen to be well sus 
tained. Also, in the Journal of the Proceedings of the Linnzat 
Society, 2. p. 34, Mr. Bentham “calls to mind how frequently 
large American genera (such as Hupatorium, Aster, Solidago, 
lanum, &¢.) are represented in Eastern Asia by a small num 
of species, which gradually diminish or altogether disappear 4 
we pr westward toward the Atlantic limits of foot 
_ whilst the types peculiar to the extreme west of Europe ( ud- 
ing of course the Arctic flora) are wholly deficient in Americ#. 
