22'J EUPHORBIACEAE. 



Family yS. EUPHORBIACEAE St. Hill. Si'URo: F.amii.v. 



Flowers not in an involucre ; calyx of several sepals. 

 Petals present, at least in the staminate flowers. 



Stamens 6; filaments distinct. i. Croton. 



Stamens lo; filaments monadelphous. 2. Ditaxis. 



Corolla wanting; stamens 1-3. 3- Tragia. 



Flowers in involucres ; calyx represented by minute scales at the base of filament- 

 like pedicels. 

 Glands of the involucres with petal-lil<e appendages ; these however sometimes 

 much reduced. 

 Leaves all opposite. 



Glands of the involucres 4 ; leaves inequilateral, usually oblique at the base. 



4. Chamaesyce. 

 Glands of the involucres 5 ; leaves equilateral, not oblique at the base. 



5. Zygophyllidium. 

 Leaves alternate or scattered, at least below the inflorescence ; bracts petal- 

 like. 6. DlCIlROPHYLLUM. 



Glands of the inflorescence without petal-like appendages ; entirely naked 



or with a crescent-like horn. 

 Stem topped by an umbel ; stipules none ; involucres in open cymes, each 



with 4 glands and entire or toothed lobes. 7. Tithymalus. 



Stem not topped by an umbel ; stipules gland-like ; involucres in cluster-like 



cymes ; each with a single gland or rarely with 4 glands and fimbriate lobes. 



8. POINSETTIA. 



I. CROTON L. 



I. Croton texensis (Klotzsch) Muell. Arg. In sandy soil from 111. and 

 Wyo. to Ala. and Ariz. ; also in Mex. — Alt. 4000-6000 ft. — New Windsor ; 

 Crow Creek ; Canon City ; Longmont ; Boulder ; La Salle. 



2. DITAXIS Vahl. 



I. Ditaxis humilis (Engelm. & Gray) Pax. {Argythamnia htimilis Muell.) 

 On prairies from Kans. and Colo, to La. and Tex. — " Southern Colorado." 



3. TRAGIA. 



I. Tragia ramosa Torn In dry soil from Mo. and Colo, to Tex. and Ariz. ; 

 also Mex. — Alt. 4000-6000 ft. — Boulder; Denver; Castle Rock; Larimer Co.; 

 Arboles; Walsenburg; Trinidad; Horsetooth Gulch; Spring Cafion; gulch 

 west of Pennock's ; Ute Creek ; Pcnnock's ; Spring Canon. 



4. CHAMAESYCE S. F. Gray. Spurge. 

 Leaves entire. 

 Annuals or biennials. 



Plants prostrate; leaf-blades nearly orbicular. i. C. serpens. 



Plants more or less ascending or erect ; leaf-blades linear or linear-lanceolate. 

 Capsule less than 1.5 mm. long. 2. C. revoluia. 



Capsule about 2 mm. long or more. 



Appendages of the glands conspicuous, white. 3. C. petaloidea. 



Appendages inconspicuous, greenish-white, or obsolete. 



4. C. Hagelliformis. 

 Perennials. 



Leaves glabrous. 



Glands transversely oval ; appendages fan-shaped, white, petalloid. 



5. C. albomarginata. 

 Glands oval ; appendages crescent-shaped, much narrower than the gland, 



greenish. 6. C. Fendleri. 



Leaves pubescent. 7- C. lata. 



