471 
will at once show that the latter is apparently identical with Z. 
populoides, which supposition is supported by the fact that they _ 
were both found in the same geological horizon (Dakota group) 
near Morrison, Colorado. The one difference between them is the 
winged petiole which is such a prominent characteristic in our, 
specimen. Its absence in Lesquereux’ specimens is doubtless to 
be accounted for by the imperfection of his material, but a close 
examination of his fig. 2 will show that there is a widening of the 
petiole where it is broken off, which evidently indicates the exist- 
“nce of similar appendages. 
: Finally I would call attention to a point which may have con- 
siderable Significance in relation to the theory of the origin of 
Stipules Previously outlined. The specimens which are the sub- 
Jéct of our illustration apparently represent a large mature leaf and 
“smaller immature one. In the mature leaf there is a distance of 
about three-eighths of an inch between the base of the leaf blade 
and the beginning of the winged appendages, while in the young 
leaf they are in juxtaposition, conditions which are to be ex- 
Pected if our theory of their origin is the correct one. 
N OTE.—Since writing the above Dr. Britton has called 
aoe attention to the following, which is of peculiar significance in 
this connection: : 
The late Dr. Thomas Morong, in his manuscript of “ The. 
Smilaceze of North and Central America,” in speaking of the spe- 
“les. which climb by means of tendrils growing from stipular wings 
°n each side of the petiole, uses these words in a foot note: “De 
dolle regards this appendage as more in the nature of a modi- 
ed leaf segment or leaflet than a stipule, but it seems to me that 
4 Stipule is nothing else than a leaflet at the base of a petiole.”* 
\ 
Two Species of Oxalis. 
mS Joun K, SMALL. 
(PLATES 222 AND 223.) | 
For several seasons during my excursions through portions of 
‘he Southern States I have met with a peculiar little Oxalis, 
-*See Bull. Torr, Club, 21: 419: Rares : 
