266 
usually been regarded by authors as forms or varieties of that 
species, but as often happens, the “ forms” or “ varieties ’’ possess 
excellent specific characters which for one reason or another have 
been overlooked. 
A study of the material in the herbaria of Mr. Eugene P. 
Bicknell and Columbia University, together with field observations 
during several seasons, have led me to the following conclusions ; 
There are two perfectly distinct species, native in eastern 
North America, which have been indiscriminately referred to the 
names O-alis corniculata or O. stricta. O-xalis corniculata is thought . 
to be a native of southern Europe or tropical America and ap- 
pears to be circumtropical. It is introduced to some extent into 
temperate regions, and we know it as a common weed in some of 
our southern cities; normally it is a prostrate and creeping plant, 
commonly wiry and very characteristic in habit, quite distinct 
from its two native eastern North American relatives with which 
we are at present concerned. 
Linnaeus defines* O. corniculata and O. stricta, giving as char- 
acters for the former; caule ramoso diffuso, pedunculis umbel- 
liferis, Hort. Cliff. 175” and Trifolium luteum minus repens et- 
jam procumbens, Moris. hist. 2, p. 183, f. 2. t. 17. f. 2.’ For O. 
stricta he gives, ‘‘caule ramoso erecto, pedunculis umbelliferis, 
Gron. Virg. 161,” and “ Trifolium . . . corniculatum luteum majus 
rectum. . ., Moris. hist. 2, p. 184, f. 2. t. 17. f. 3.” We notice 
that Linnaeus describes the habit of the two species as dissimilar, 
while the character of the inflorescence is recorded as the same in 
both, namely, “ pedunculis umbelliferis.” 
What strikes one most forcibly in the case of our two eastern 
species is the great difference in the general habit of the plants 
and their more minute morphology; the lower stout and pale 
plant with umbel-like inflorescence, large columnar abruptly 
pointed pods and strigose pedicels is closely related to O-xalis cor- 
niculata although abundantly distinct. Its characters pointed to 
the Linnaean O. stricta, but to make sure, specimens of both the 
eastern American forms were sent to Mr. Edmund Baker, who 
kindly compared them with the originals in the herbarium of the 
British Museum of Natural History and reported that the plant 
* Sp. Pl. 435. 
