18 Contributions from the Gray Herbarium 
narrow and short-and-broad leaf-forms, and of forms with longer- 
and-spreading and short-and-appressed pubescence of leaf and 
stem. The type sheet of Viguiera Ghiesbreghtii in the Gray Her- 
barium, Ghiesbreght 381, labelled (in Dr. Gray’s hand) as from 
Morelia, Michoacan, bears two specimens, one with the hairs of 
stem and leaves longer and spreading or ascending, and a pubescent 
achene with the normal pappus of Viguiera, the other with the 
hairs more appressed and a glabrous epappose achene. The two 
specimens in the Kew Herbarium on which Hemsley’s Gymnolomia 
flava was founded, although both with the glabrous epappose 
achene of Heliomeris (‘‘ Gymnolomia’’), differ in much the same 
way as regards the pubescence, and although they bear a printed 
label signifying that they were collected by Ghiesbreght in Oaxaca, 
their resemblance to the types of V. Ghiesbreghtii is so great as 
strongly to suggest the suspicion that they were taken from the 
same colony. 
The likeness between Viguiera pachycephala and Gymnolomia | 
megacephala var. simulans is of quite the same nature, amounting 
to identity in every part but the achene. These two cases of abso- 
lute specific identity in species of the two related genera, reinforced 
by the fact that the nearly related species of Gymnolomia are (omit- 
ting achenial features) clearly identical subgenerically with the cor- 
respondingly related species of Viguiera, are capable of but one 
interpretation, viz. — that all these plants are members of the 
same genus, and that the presence or absence of pappus is here as 
elsewhere a character of no more than varietal value when unsup- 
ported by other differences. Here also is the explanation of the 
somewhat remarkable fact that no epappose species of Vigusera 
has ever been described, while the occasional absence of pappus in 
normally pappiferous species has long been recognized as of com- 
mon occurrence in many closely related genera. Those who ad- 
here to the theory on which the late Prof. E. D. Cope was wont to 
insist — that generic differentiation often precedes specific — will 
of course find no difficulty in the cases of Gymnolomia flava and G. 
megacephala var. simulans; but there seems no occasion here for 
such a dubious explanation of the observed facts when a much 
simpler one, supported by a large number of analogous cases it 
allied genera, will suffice. 


