234 PITTONIA. 
throughout Acerates is angled and notched at about the 
middle, from which point it tapers both ways. In Asclepias 
it is broadest and notched at the very base, thence tapering 
to thesummit. This character was noticed by Gray, though 
he did not accentuate it, préferring to treat the horn of the 
hood or its absence as the more important. That he was 
wrong in this judgment is demonstrated completely by the 
fact that treating the born as the more essential technicality 
he was obliged to ignore habit, and put into Asclepias a 
species which is, as he admitted, habitally an Acerates. 
And to the anther-wing character is necessarily accorded a 
higher importance because it brings together plants at per- 
fect agreement in habit. 
Coinciding with Acerates in point of their strictly lateral 
inflorescence and green flowers are two other groups of North 
American Asclepiads which must be separated from Ascle- 
pias, since they are at variance with that genus not only in 
habit but in floral characters of more importance than the 
presence or absence of the horn. One of these groups seems 
to be monotypical, and I name it, in allusion to its most 
important floral character, 
OXYPTERYX. 
Plants with habit, lateral inflorescence and subsessile um- 
bels of Acerates. Corolla reflexed in anthesis. Column 
under the hoods almost none. Hoods excessively large and 
conspicuous though dull-greenish, thin and conduplicate 
throughout though consisting of a very distinct triangular- 
lanceolate basally truncate or somewhat auriculate blade, 
and shorter narrower linear claw, the former appendaged 
near the middle with an abruptly falcate-incurved and 
acuminate crest or horn. Corneous anther-wings acutely 
triangular, broader than long, broadest at the angled mid- 
dle portion and tapering abruptly both to apex and base, 
the angle without a notch, 
