new Genera of Composita. 107 
Mountains. The generic name is expressive of its most 
striking peculiarity, that of a pappus composed of a solitary 
mose bristle ! 
Many specimens occur of that group of biennial Asters 
which form Mr. Nuttall’s genus Dieteria, and which are 
characteristic productions of the wide arid tracts which oc- 
cupy so large a space both on this side and beyond the 
. Rocky Mountains. These specimens tend to confirm the 
opinion I had already expressed,’ that three of Nuttall’s pro- 
posed species must be reduced to one. 
` Mr. Fremont’s collection also affords us a new genus in the 
yellow or homochromous series of Asteroid plants. It is a 
low shrubby plant, which furnishes a connecting link between 
several genera that accord in habit but differ in technical 
character; such as Gutierrezia (Brachyris, Nutt.), Amphia- 
chyris, and the section Euthamia of Solidago. Its disk-flow- 
a have nearly the pappus pilosus of the latter; while the 
single ray-flower exhibits the pappus paleaceus of the former: 
it the paleæ, however, are narrow, squamellate, and variously 
and irregularly concreted. Like Amphiachyris, the ray-flow- 
ers only appear to be fertile; although the ovary in those of 
the disk is fully formed. The generic name which I have - 
Chosen alludes to the combination of these two kinds of pap- 
Pus in the same plant. 
` AMPHIPAPPUS, Torr. & Gray, ined. 
Compositz-A steroidecw : Subtr. Asterinez : Div. Chrysocomee. ; $ 
Capitulum plerumque 7-florum heterogamum ; nempe, flore 
radii unico, ligulato, foemineo, fertili, et floribus disci 46 
tubulosis, hermaphroditis, sed sterilibus? Involucrum obovoi- 
I; squamis 6-7 subzequalibus, chartaceis, ovalibus, con- 
“avis, subcarinatis, appresso-imbrieatis. Receptaculum an- 
"à b : 1 Flora of North America, ii. p. 100. 
