34 
BOTANY: W. TRELEASE 
foliage internodes; and in a single known species, P. paradoxum, the 
stem is made up of rather terete joints with cataphyls and ancipital 
joints without them, in regular alternating succession. 
In the geographic distribution of its species, Phoradendron is rather 
unusually instructive. The genus is strictly American and extends 
from Washington, Colorado, the mouth of the Ohio River, and southern 
New Jersey to the Southern Argentine region on the continent, and 
through the entire West Indian chain; one species occurs in the Pacific 
island Guadalupe, and two are found in the Galapagos group of Pacific 
islands, — both oceanic but with American floras. None of its many 
species of fairly homogenous character possesses a very wide geographic 
range. Marked examples of widespread occurrence are afforded only 
by a few such polymorphous species as what is usually called P. lati- 
folium, or an assemblage of intricately related if differentiable species 
like that usually known as P. rubrum or P. quadr angular e, both of which 
range from Brazil to Central Mexico and well through the West Indies. 
Few species, indeed, equal in range our native P. flavescens, which occurs 
from southern New Jersey to the lower Wabash, Oklahoma and eastern 
Texas, reaching southeast to the Gulf and ocean. 
Admirably endowed with means of free dissemination through its 
edible berries with extremely viscid pulp, which leads to their dispersal 
by birds, these mistletoes seem limited nevertheless to a surprising 
extent by ordinary barriers to plant migration. Like the similar Euro- 
pean Viscum album, with its scarce-definable races capable of effective 
germination only on the host-species from which the seed came, our 
eastern P. flavescens though attacking a large variety of host plants 
is usually found confined to a single host in a given region, and such 
experiments as have been made on it show that it can be transferred 
from one host to another with difficulty if at all. How far this may be 
concerned in the polymorphism of this species and how far its Kke may 
serve to limit the dispersal of most species is at present a matter of con- 
jecture only. 
Viewed on broad geographic lines, the species of Phoradendron usually 
occupy areas that present severally an assemblage of fairly uniform 
meteorologic features with limiting environment, — in this respect agree- 
ing with most other plants and with animals. In the main, the regions 
affected by individual species of Phoradendron are the following: 
North America: (1) Atlantic, (2) Rocky Mountain, (3) Pacific, (4) 
Great Basin or Sonoran, — in the United States; (5) Table-land, (6) 
Eastern or Western Sierra Madre, (7) Western riparian, (8) Yucatecan, 
and (9) Cordilleran, — in Mexico and Central America. 
