1904 | NELSON: ROCKY MOUNTAIN PLANTS 261 
whole matter very fully in the fifth of that series of papers entitled 
‘Observations on the Compositae” (Erythea 2: 71). In his 
discussion of the asteroid genera (Erythea 2: 53) it seems to me 
that he was at his best, and gave usa bit of botanical philosophy 
that must stand for all time. But the criterion there laid down, 
and now generally accepted, as marking the limits of genera, 
confirms Stenotopsis as a valid genus. Into this genus another 
species must therefore find its way as follows: 
‘Stenotopsis McLeanii, n. n.—A/lopappus McLeanii T. S. Brand- 
egee, Bor. Gaz. 27: 448. 1899; Stenotus McLeani Heller, Muhlen- 
bergia 1: 7. 1900. 
There are three other plants that seem to me to form an equally 
good and homogeneous group. One of these, starting as Stenotus 
pygmaeus (T. & G. Fl.), passed into Aplopappus (Gray Syn. Fl.) 
and was there associated with a near relative, Aplopappus Lyallit 
Gray. Greene in his discussion of the segregates of Aplopappus 
(Erythea 2:) considers the status of the former of these two and 
decides that it has enough Macronema characters to justify its 
transfer to that genus. Recently, however, it has been distributed 
on Greene’s determination as Stenotus (Pl. Baker, 1899), though 
this may have been a clerical error. The second of these species 
Greene either overlooked or ignored entirely. But now Rydberg 
(Mem. N. Y. Bot. Gard. 1: 382. 1900) after due consideration 
very reluctantly makes the second Pyrrocoma Lyalli. Henderson, 
apparently not accepting the segregates of Aplopappus, describes 
(Bull. Torr. Bot. Club 27: 347. 1900) a third species which he 
pronounces ‘close to A. Lyallii as well as to A. pygmaeus.” With 
these doubts and these differences of opinion staring us in the 
face, why not again accept the criterion laid down by Greene 
(that is, if I interpret him aright, a genus may be founded on 
characters of habit, along with characters of the vegetative organs 
and morphological characters of the flower, but not upon 
morphological characters of the flowers alone in the face of 
differences in habit and of the vegetative organs) for the limita- 
tion of genera, and thus bring together under one name these 
species which are allied by habit and morphological characters 
to each other and are aberrant in any recognized genus or genera 
in which they can be placed. 
