RvDBERG : Rocky Mountain flora 145 



Chamaesyce rugulosa (Engelm.) Rydb. 

 Euphorbia scrpyllifolia rugulosa Engelm. ; Millsp. Pittonia 2:85. 

 1890. 



Chamaesyce albicaulis Rydb. 

 Euphorbia albicaulis Rydb. Aleni. N. V. Bot. Gard. i : 266. 1900. 



Tithymalus arkansanus coloradensis (Norton) Rydb. 



Euphorbia aikaiisaiia coloradensis Norton, Rep. Missouri Bot. 

 Gard. II : 105. 1900. 



Sida sagittaefolia (A. Gray) Rydb. 

 Sida Icpidota sagittaefolia A. Gray, PI. Wright, i : i§. 1852. 



Sphaeralcea marginata York, sp. nov. 



Perennial, herbaceous ; stetn 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 ^^- ^^'ide, 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 : caly.N-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 

 10-12 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 Mu)i- 

 roaiia (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 5. ineana 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. 



