308 EUPHORBIACEAE (SPURGE FAMILY) 



keel conspicuous: the 2-lobed caruncle half the length of the seed. Colorado 

 and eastward across the plains. 



1. Polygala alba. Nutt. Gen. 2: 87. 1818. Smoothish, about 3 dm. high, 

 leafy half-way to the summit: leaves linear to oblanceolate, margins slightly 

 iv volute: flowers deciduous, leaving the rachis roughened after their fall; 

 white : seed with caruncle extended into 2 ear-like lobes nearly as long as the 

 seed. Plains of the upper Missouri. 



64. EUPHORBIACEAE St. Hil. SPURGE FAMILY 



Herbs, shrubs, or trees, usually with milky or purplish acrid sap and monoe- 

 cious or dioecious flowers. Leaves either opposite, alternate, or whorled, with 

 or without stipules. Flowers with or without floral envelopes; if the calyx is 

 wanting then a calyx-like involucre is present. Ovary 3-celled, with a pendi 

 lous ovule in each cell, maturing into a 3-celled elastically dehiscent capsul 

 with crustaceous seeds. Stamens few or numerous, the filaments free or united. 

 Styles and stigmas as many as the cells of the ovary. 



Flowers with a true calyx. 



Pubescence stellate 1. Croton. 



Pubescence simple. 



Flowers with petals . . . 2. Ditaxis. 



Flowers apetaious .......... 3. Tragia. 



Flowers in an involucre, no true calyx 4. Euphorbia. 



1. CROTON L. 



Herbs or shrubs, scurfy or stellately hairy or sometimes glandular: leaves 

 alternate, entire or repand. Staminate calyx 4-6-parted. Petals often pres- 

 ent but small or rudimentary, alternating with the glands of a central disk. 

 Stamens 5-many, on a hairy receptacle. Pistillate calyx usually 5-parted, but 

 the petals mostly obsolete. Seeds smooth and shining, carunculate. 



1. Croton texensis (Klotzsch.) Muell. Arg. in DC. Prodr. 15: 692. 1862. 

 Covered with a close, canescent, stellate pubescence, dichotomously branched 

 or spreading, 3-6 dm. high: leaves lanceolate, oblong, or linear-lanceolate: 

 dioecious; racemes of staminate flowers short: ovary stellate-tomentose; 

 styles twice or thrice dichotomously 2-parted. From Wyoming to Colorado 

 and southward. 



2. DITAXIS Vahl. 



Erect herbs or shrubs with purplish sap. Leaves (in ours) entire, alternate, 

 usually stipulate. Calyx valvate in the staminate flowers, imbricate in the 

 pistillate. Petals 4 or 5, alternate with the calyx-lobes and with the lobes 

 of the glandular disk. Filaments united into a central column. Seeds sub- 

 globose, roughened or reticulated, not carunculate. 



1. Ditaxis humilis (Eng. & Gray) Pax, in Engl. & Prantl, Nat. Pfl. Fam. 

 ;>"': -I."). is'.H). Stem about 3 dm. high, much branched, silky or strigose- 

 pubescent, branches spreading: leaves narrowed at the base, spatulate or 

 obovate, lanceolate or linear-lanceolate, acute, sparingly pubescent: raceme 

 much shorter t lian I he leaves, on very short peduncles. Argythamnia humilis. 

 Colorado, southward and eastward. 



3. TRAGIA L. 



Mivft or j-limliiiiK plants, pubescent or hispid, sometimes stinging, with 

 mostly alternate, stipulate leaves. The sterile flowers above, the few fertile 

 at tin l>a-e, all with small bracts. Staminate calyx 3-5-parted; filaments 



