232 PITTONIA. 
nineleenth-century authorities—this breaking up of their 
one genus into a natural family—is doubtless expedient, and 
must continue to stand approved. But I conceive that the 
real principles upon which the segregation of genera has 
proceeded, and may still proceed further, have not been 
sufficiently looked into. 
It is not only in respect to their fruit that Asclepias and 
the many genera that have now been segregated from it are 
quitealike. They havethe same umbelliform inflorescence, 
the same calyx, the same corolla, the crown only excepted, 
and they are treated asif at no notable disagreement among 
themselves even as regards their stamens and pistils. 
' It is, as I have just intimated, in the corona of the perianth, 
with its interesting diversities in the minutize of its confor- 
mation, that so many characters of supposed generic value 
have latterly been detected. To some of these modifications 
of the corona a fanciful and exaggerated importance has been 
attached ; as for example to that diminutive organ which 1$ 
commonly known as the horn of the hood. It is easy to 
note the presence or absence of such an organ; and because 
it is easier than to recognize, or teach to recognize, a differ- 
encein habit,thereforeeven the professed systematistis under | 
a temptation to rely upon it as an essential generic char- 
acter; to magnify itsimportance. It was Linneus, the most 
unnatural and artificial of systematists, who indicated the 
horn of the hood as the character of Asclepias; and yet, 8 
hundred years after Linnæus, men like Bentham and Asa 
Gray, professedly ignoring artificialism in taxonomy, are 
more absolute artificialists than Linnæus himself when they 
come to the treatment of Asclepias and its allies; for they 
both make the horn the absolute and only mark of Asclepias, 
which Linneeus, after all, had too much of the sense of what — 
is natural and rational in classification to carry into effect. | 
He does indeed name the horn as a character of the genus, — 
yet, out of his eighteen species of Asclepias, only eleven have — 
it; the other seven being destitute of any trace of it. Ana - 
