224 EUPHORBIACEAE. 



12. Chamaesyce stictospora (Engelm.) Small. (E. stictospora Engelm.) 

 On prairies and plains from Kans. and Colo, to Mex. and Ariz. Alt. 5000- 

 7000 ft. Canon City; Pueblo; south of Fort Collins. 



5. ZYGOPHYLLIDIUM Small. 



i. Zygophyllidium hexagonum (Nutt.) Small. (Euphorbia hexagona Nutt.) 

 In river valleys from Iowa and Mont, to Tex. and Colo. Plains near Denver. 



6. DICHROPHYLLUM Kl. & Garcke. SNOW-ON-THE-MOUNTAIN. 



i. Dichrophyllum marginatum (Pursh) Kl. & Garcke. (Euphorbia mar- 

 ginata Pursh) In pastures from Minn, and Mont, to Tex. and Colo. Alt. 

 4000-7000 ft. Rocky Mountains; Boulder; sources of the Platte; Fort Col- 

 lins; New Windsor; Dry Creek, Larimer Co.; La Veta; Denver; Nepesta. 



7. TITHYMALUS Kl. & Garcke. SPURGE. 



Leaves entire ; glands of the involucres with processes. 

 Plants perennial ; processes short and blunt. 



Stem-leaves linear; capsule rough; seeds smooth. i. T. Cyparissias. 



Stem-leaves from oblong or oblanceolate to orbicular ; capsule smooth ; 



seeds pitted. 



Bracts rhombic-ovate, cuspidate ; stem rather slender. 2. T. monianus. 

 Bracts rhombic-reniform, mucronate ; stem stout. 3. T. robustus. 



Plants annual ; processes of the glands long and horn-like ; seeds pitted. 



4. T. crenulatus. 

 Leaves distinctly serrulate ; plants annual or biennial ; glands without processes. 



Upper stem-leaves merely sessile ; bracts manifestly longer than broad. 



5. T. arkansanus. 

 Upper stem-leaves with small basal lobes ; bracts mostly broader than long. 



6. T, missouriensis. 



1. Tithymalus Cyparissias (L.) Lam. (Euphorbia Cyparissias L.) Escaped 

 from cultivation from. Mass, and Colo, to Va. Fort Collins. 



2. Tithymalus montanus (Engelm.) Small. (Euphorbia montana Engelm.) 

 On dry hills from Colo, and Utah to Tex and Ariz. Alt. 6000-8000 ft. 

 Cimarron; Buena Vista. 



3. Tithymalus robustus (Engelm.) Small. (E. montana robusta Engelm.) 

 On dry hills from Mont, and S. D. to Colo, and Ariz. Alt. 4000-8000 ft. 

 Cimarron ; Cucharas River, La Veta ; Colorado Springs ; Alamosa ; Larimer 

 Co. ; Gunnison ; Arboles ; Fort Collins ; Longmont ; Pike's Peak trail ; Poudre 

 River; Fort Collins; along Purgatory River; Fossil Creek; Rist Canon; 

 Colorado Springs. 



4. Tithymalus crenulatus (Engelm.) Heller. (E. crenulata Engelm.) On 

 hillsides from Colo, to Calif, and Ariz. Mancos ; Horsetooth Gulch. 



5. Tithymalus arkansanus (Engelm. & Gray) Kl. & Garcke. (E. arkansana 

 Engelm. & Gray) In dry soil from Mo. and S. D. to Ala. and Ariz. Alt. 

 4000-6000 ft. Larimer Co.; Boulder; Horsetooth Gulch. 



Tithymalus arkansanus coloradensis (Norton) Rydb. Floral leaves ellip- 

 tical. McElmo Canon; Larimer Co. 



6. Tithymalus missouriensis (Norton) Small. (Euphorbia dictyosperma 

 Coulter; not F. & M. ; E. arkansana missouriensis Norton) In sandy soil 

 from Iowa and Wash, to Kans. and N. M. Denver. 



