[ 401 ] 
XXI. On the Eriogonex, a Tribe fof the Order Polygonacee. By GEORGE 
Bentam, Esq., F.L.S. 
Read April 7th, 1835. 
THE genus Eriogonum was first established by Michaux in his Flora Boreali- 
Americana, upon a Carolina plant distinguished from other Polygonacewe, not 
so much by the organs of fructification, which are not very essentially different 
from those of Rheum, as by the involucrate inflorescence and the absence of 
the ochrec, or sheathing stipules, observable in some shape or other in every 
other genus of the order. To the single species described by Michaux (E. to- 
mentosum), Nuttall and Pursh added two others gathered by the former botanist 
in the plains of the Missouri (E. flavum and E. pauciflorum), and Smith in 
Rees’s Cyclopedia described two more brought by Menzies from the coast of 
California (E. latifolium and E. parvifolium). These five North American 
species have now been increased to thirty-three by the discoveries of Mr. 
Douglass in New California and the North-west district, and of Mr. Nuttall, 
Dr. Torrey, Mr. Drummond, and others, in the Rocky Mountains, Arkansa 
territories, and province of Texas; and all are equally distinguished by their 
involucrate inflorescence and absence of stipulz, at least to the lower or true 
cauline leaves. But a considerable difference in habit has induced me not 
only, at the suggestion of Mr. Brown, to separate generically five species with 
uniflorous involucres, but, amongst these, to isolate one (Mucronea), which 
has a compressed and bidentate involucre formed of two leaves, instead of a 
triangular sexdentate one formed of six leaves, as in the other four species 
(Chorizanthe, Br.). The latter genus is further confirmed and augmented by 
seven species collected in Chili by Macrae, Cuming, Bridges, &c., giving a 
total of forty species comprised in the three genera. 
The whole of these plants have all the essential characters of Polygonacee, 
thus stated by Brown (Prodr. p. 418) : 
