-24 EUPHORBIACEAE. 



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

 On prairies and plains from Kans. and Colo, (o 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-ox-the-mountaix. 



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 vi'ith processes. 

 Plants perennial ; processes short and blunt. 



Stem-leaves linear; capsule rough; seeds smooth. 1. T. Cyparissias. 



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

 seeds pitted. 

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

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



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



4. T. crenulatiis. 

 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 Caiion ; 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. 



