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M. L. FERNALD 
floras in the remotest corners of the globe. The best known of these 
discontinuous floras is, of course, the case of temperate eastern America 
and temperate eastern Asia, which together share scores of genera and 
subgenera and even a unique family unknown in other parts of the 
world, while many more species and geographic varieties are confined 
to these two most remote regions. This famous group of plants, long 
ago pointed out by Asa Gray, may be illustrated by the tulip-tree, 
Liriodendron Tulipifera (fig. ii), with two living areas, one from New 
England to the Great Lakes and the Gulf of Mexico, the other (of 
var. chinense) in China. Very similar ranges are displayed, though 
often with greater development in Asia, by genera such as the mono- 
typic Symplocarpus (fig. 12), by Magnolia, Menispermum, Podophyl- 
lum, Caulophyllum, Panax, Phryma, and numerous others. In fact, 
so frequent is this identity that we are now discovering upon close 
inspection that common Alleghenian plants, which have long been 
identified with continental European species, are in reality quite 
distinct from the European but inseparable from their eastern Asiatic 
representatives. Thus the common Alleghenian enchanter's night- 
shade, which for a century and a half has passed as the continental 
European Circaea lutetiana, proves to be not that species but to 
identical with the plant of eastern Asia. The disrupted range of this 
species, C. latifolia, is essentially like that of Symplocarpus foetidus. 
Very recently other cases have come to attention. For instance, 
Butters, in studying certain widely diffused groups of ferns, discovered 
that in its essential character the common lady fern of eastern America 
which has generally been considered the European Athyrium Filix- 
femina, is really very different and constitutes a distinct east-American 
species, A. angustum, but that collections from China and Amur show 
fronds quite inseparable from the east-American plant. Again, in 
his studies of the variations of Botrychium virginianum. Butters found 
pronounced characters in the sporangia, which separate the European 
plant as var. europaeum, but that the typical B. virginianum of tem- 
perate eastern America reappears in China. 
Other plants of much broader and almost general occurrence 
throughout temperate Eurasia are found in America only at the ex- 
treme eastern margin of the continent. Such a species is Stellaria 
uliginosa of wide Eurasian range, and found locally in springy spots 
from Newfoundland to Maryland. Of more restricted American 
range is Potamogeton poly gonif alius, generally dispersed over Eurasia 
