236 PITTONIA. 
exserted. Anther-wings (wholly as in Acerates) broadest, 
and notched, in the middle, thence tapering both ways. 
. P.toneicornv. Asclepias longicornu, Benth. Pl. Hartw. 
M (1840). An almost exclusively Mexican species, the only 
specimen seen by me from within the U. S. being one in the 
U. S. Museum obtained in southwestern Texas in 1891 by 
J. E. Bodin. All the so-called A. longicornu of New Mexico 
and Arizona is plainly referable to other species. The es- 
sential floral characters of the present species are the greatly 
elongated and narrow solid basal part of the hood, and the 
distinctly angled (semi-rhombic) anther-wing. 
2. P. LiNDHEIMERI. Asclepias Lindheimeri, Engelm. & 
Gray, | Pl. Lindh. 250 (1845). A Wrightii, Greene, in Gray, 
Proe. Am. Acad. xvi, 102 (1880) Frequent in western 
Texas and southern New Mexico. Plant lower, stouter and 
more nearly glabrous than P. longicornu, with shorter hoods, 
but very definitely distinguished by its rounded (semiovate) 
rather than angular anther-wings. It is to be noted that 
Dr. Gray finally referred his A. Lindheimeri to longicornu, 
and my A. Wrightii to nyctaginifolia. But all the P. Lind- 
heimeri and A. Wrightii that I have now been able to com- 
pare are at absolute agreement in all points, and quite dis- 
tinet from all others as to hoods and anther-wings. These 
latter have here the usual notch near the middle, but their 
outline is nevertheless as a whole curved and not angular; 
and this semiovate character was indicated in the original 
diagnosis of A. Wrightii. 
3. P. HELLERI. Glabrous, leafly from the base, but flo- 
riferous only near the summit: leaves thin, from deltoid- 
ovate to oval, only 2 or 3 inches long, on petioles of nearly 
an inch: flowers large as in the foregoing: hoods long, 
about twice the length of the anthers, their amply laminated 
upper part as long as the solid basal part: anther-wings 
thick, semi-rhombic. 
