YALUE OF CHARACTERS. 845 
have, generally speaking, regarded them as absolute for the di- . 
stinction of genera. Schultz Bipontinus, however, in some of his 
later generic changes, has shown a disposition to neglect them, 
apparently from having observed their little accordance in certain 
cases with generic groups he was disposed to form on other 
grounds. But I have been unable to ascertain how far he 
generalized this degradation of the character. My own observa- 
tions would lead me to conclude that, like other characters, sexu- 
ality varies in value in different tribes and in different genera, in 
a few cases absolute even in tribes, often of considerable impor- 
` tance in genera, but often also specific only, or at most available 
for sections or artificial groups of species. 
These sexual differences relate to those of the individual flowers 
or florets within the head, and those of the flower-heads taken 
generally. 
With regard to the individual florets, it is usual to distinguish 
four kinds—hermaphrodite, male, female, and neuter; but the 
sterility of the pistil is often so uncertain or variable in the 
anther-bearing flowers, in which it is never absolutely deficient, 
that I have found it much more convenient to designate as 
hermaphrodite all florets having perfect anthers, whether their 
pistil be susceptible of fertilization or not, distinguishing them as 
fertile or sterile—and as female all florets in which the anthers are 
abortive or deficient and the style is present; the neuter florets, 
reduced to a corolla with a rudimentary scarcely distinet ovary, 
might be classed in the same category as the females, as the 
abortion of the style is sometimes gradual or uncertain. Thus 
reducing the kinds of florets to two when both occur in the same 
head, the hermaphrodite ones invariably occupy the centre, the 
females being placed in one or more concentric rows in the cir- 
cumference. Nuttall bad indeed published a genus which he 
characterized from the supposed singular inversion of this position, 
the females being, as he believed, in the centre, surrounded by 
males, and gave it, therefore, the name of Parastrephia; but 
upon inspecting the original specimen in Nuttall’s herbarium (a 
mere fragment gathered by Curson near Arequipa) it appeared to 
me that he had been deceived by some degree of unisexuality in 
the flower-heads, some having nearly or perhaps all the florets 
female and therefore central as well as cireumferential, whilst one 
of the heads appeared to be entirely hermaphrodite. There are 
not heads enough on the specimen to verify the fact; but I at 
