486 CocKERELL: NorTH AMERICAN SPECIES OF HYMENOXYS 
which have been gathered for the extraction of rubber show it to 
be no less uniform near the northern limit of its range. This 
refers of course to the gross characters; there is much variation 
in small details. Dr. Greene thus characterizes P. floribunda: 
“Taller and more slender than P. Richardsonii, the wool at base 
of stem more silky ; stems repeatedly branched; heads many times 
more numerous, of less than half the size, forming a broad flat- 
‘topped inflorescence ; paleae of the pappus lanceolate, some slen- 
derly acuminate, others not so.” 
The distribution of the species includes the southern half of 
Colorado, at comparatively high altitudes on the west side of the 
front range; northern New Mexico, as far east as Raton, and the 
region about San Francisco Mountain, Arizona. The characters 
of the forms of H/. floribunda, and of the allied 7. Earlei, may be 
compared as shown in the table on the opposite page. 
H. Earlei, by its rather peculiar appearance and especially the 
cut of its foliage, appears to be a valid species. The other three 
are unquestionably races of one species (47. floribunda). The 
original description of H. floribunda utilis (PLare 20) under the 
name licradenia floribunda utilis (Bull. Colo. College Museum, 
No. 1, December 11, 1903) is as follows : 
‘‘ Similar in appearance and mode of growth to P. floribunda 
(a topo-type collected by Heller at Santa Fé, N. M., compared) 
but easily distinguished by the pale yellowish, broad and subovate 
outer bracts, with strongly concave outer margins, and the back 
conspicuously keeled ; these bracts are united about to the middle. 
(In P. floribunda these bracts are greener, long and pointed, with 
straight sides, and not united quite so far as the middle). The 
disc-corollas have a rusty-red ring in the throat, which appears to 
be absent in floribunda, Rays narrower, about 2 mm. in diameter. 
As far as the specimens seen go, the basal part of the stems is 
much more robust in wfilis than floribunda. 
" Compared with P. macrantha and P. ligulaeflora, the rubber 
plant differs conspicuously in its taller stature and smaller flowers. 
It is also readily distinguished from P. Davidsoni and the other 
described species of the genus. In P. Davidsoni (cotype examined) 
the outer bracts are narrower and shorter than the inner, and the 
inner are much more pointed than those of utilis, The disc-corollas 
of Davidsoni are considerably broader at the top than those of 
utilis. The length of the disc-corollas in Davidsoni is 344 mm.,in 
utilis and floribunda 4, in ligulacfora 5. In P. Ligulaefora and 
