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RYDBERG: Rocky MounNTAIN FLORA 145 
Chamaesyce rugulosa (Engelm.) Rydb. 
Euphorbia serpyllifolia rugulosa Engelm.; Millsp. Pittonia 2: 385. 
1890. 
Chamaesyce albicaulis Rydb. 
Euphorbia albicaulis Rydb. Mem. N. Y. Bot. Gard. 1: 266. 1900. 
Tithymalus arkansanus coloradensis (Norton) Rydb. 
Euphorbia arkansana coloradensis Norton, Rep. Missouri Bot. 
ard. 2%. 405. 1900. 
Sida sagittaefolia (A. Gray) Rydb. 
Sida lepidota sagittacfolia A. Gray, Pl. Wright. r: 18. 1852. 
Sphaeralcea marginata York, sp. nov. 
Perennial, herbaceous ; stem usually branching from the base, 
with ascending branches, 2-6 dm. tall, densely stellate-canescent ; 
leaf-blades subrotund, rounded-ovate or subcordate, 1.5-4 cm. 
long, 1.5—3 cm. wide, cordate or truncate at the base, crenate or 
imperfectly dentate, slightly 3—5-lobed, the middle lobe acute or ob- 
tuse, the upper surface with close stellate pubescence, more densely 
pubescent beneath, petioles less than % as long as the blades or 
sometimes longer ; flowers borne in narrow panicles ; involucre of 
3 small setaceous bracts: calyx-tube densely stellate-pubescent, 
about 3 mm. long; lobes 5, ovate, acute or acuminate, almost 
glabrous or sparingly stellate-pubescent on dorsal surface, densely 
pubescent on the margin, glabrous within, 2-3 mm. long, in fruit 
4-5 mm. long; petals pink, obovate, 10-12 mm. long ; carpels 
10-I2 in number, 3—4 mm. long, cuspidate, the lower half reticu- 
lated ; ovules two; usually only one seed developed in the lower 
part of each carpel, upper part somewhat aborted ; seeds reniform, 
glabrous. 
In general appearance this plant resembles Sphaeralcea Mun- 
roana (Doug.) Spach; but in the former, the mature carpels sepa- 
rate from the central axis by a small thread attached to the base 
of each carpel, while in the latter, the carpels do not separate 
from the central axis by a thread. Sphaeralcea marginata also 
resembles S. incana Torr.; but the latter is taller, the leaves are 
larger, the pubescence on both sides of the leaves is much denser 
and finer, the paniculate clusters of flowers are longer and more 
open and the carpels are nearly always two-seeded. 
