VARIATIONS OF SPECIES. 353 
twice as /all, which, happily, refers to the most nearly re- 
lated species, Bidens cernua. While collecting along the 
alluvial, marshy borders of the Potomac below Alexandria, 
some years ago, we found this species (not before discovered 
so far south) growing to the extraordinary height of five 
feet. This, compared with Gray's maximum height, will be 
seen to be in the ratio of six to one ; while in the instance 
of B. chrysanthemotdes, it was only three and a half to one. 
Our press would barely admit of smaller branches, while in 
collecting the same species in New York, we nave easily 
pressed two entire plants side by side. As if this were not 
a sufficiently surprising effort of nature, on proceeding some 
distance farther, we came upon some plants of Oxalis stricta 
(an eccentric plant in more than one respect) fully five feet 
in height, and widely branched. We do not apprehend that 
such statements will be discredited by any person familiar 
with the vegetation of such localities. We mention them as 
curiosities in vegetable growth, and not as matters worthy 
of permanent rocorii or of a place in a work of the nature 
of the " Manual." 
Such variations in the size of plants appear to be seldom 
attended with any material change of specific characters, and 
are therefore of less interest than those produced by differ- 
ence of latitude and longitude, or by change of station, as 
from wet to dry locations, from sunny exposures to shade, 
from marine to fresh-water localities, or from mountain to 
valley, and vice versa. These are all fertile in effects of the 
greatest interest to modern theorists, and no botanist should 
fail to make them a subject of special study. Such observa- 
tions inevitably suggest a former unity of many of our spe- 
cies and genera, Mid result in the correction of too wide 
distinctions. The two species of Bidens referred to, to- 
gether with B. connata, are strongly suggestive of a common 
parentage; and when Bidens frondosa is compared with 
Coreopsis bidentoides (especially since the former has been 
found with upwardly barbed awns), it is difficult to perceive 
AMER. NATURALIST, VOL. IV. 
