ON THE CLASSIFICATION OF ASCLEPIADS. 235 
1. O. ARENICOLA. Asclepias arenicola, Nash. Bull. Torr. 
Club. xxiii. 252 (1896). While the plant as a whole would 
be taken when out of flower for nothing else but an Acerates, 
the flower itself is structurally farther removed from that 
genus than is even Asclepias itself. The hoods, as much 
shortened, reduced and put out of sight, as it were, in Ace- 
rates, are here become the conspicuous part of the flower, 
being elongated so as far to supersede the other organs, and 
dilated to resemble petals, besides being more distinctly than 
in any other of our Asclepiads differentiated into blade and 
claw. The form of the anther-wing in Ozypteryz is perfectly 
unique, being broadest and acutely angled in the middle, 
and quite destitute of the notch which marks imvariably all 
the species of both Asclepias and Acerates. 
Another natural genus, and one which I have for twenty 
years regarded as such, has for its type the Asclepias longi- 
cornu of Bentham. The plants are far more nearly related 
to Acerates than to Asclepias, having the low stature, broad 
foliage and strictly lateral inflorescence of subsessile umbels 
of green flowers that mark Acerates. They have for their 
most important technical mark exactly the anther-wings of 
` that genus, yet are widely separated from it, and also from 
Asclepias by other points of floral structure. As the type- 
species has been assigned a subgeneric name, I shall employ 
that name for the genus as such. 
PODOSTEMMA. 
Plants stout and low, leafy and floriferous from the base, 
the umbelliform clusters exclusively lateral and subsessile 
(as in Acerates), but the flowers few and large (as in Asclepio- 
dora). Hoods excessively elongated, far exceeding the an- 
thers, mainly solid (as in Anantheriz, i. e., Anthanotis), but 
hear the iit laminately dilated, and here bearing usually 
two horns, one short and included, the other long and well 
