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WOOTON AND STANDLEY FLORA OF NEW MEXICO. 



393 



81. EUPHORBIACEAE. Spurge Family. 



Monoecious or dicocious herbs or shrubs with acrid or milky sap; leaves simple, 

 sessile or petiolate, alternate or opposite; stipules present or wanting; inflorescence 

 various, the flowers in volu crate in one section, the involucre resembling a calyx 

 and the true calyx much reduced; number of parts of the perianth varying in the 

 stamina te and pistillate flowers in the same species; corolla often wanting, especially 

 in pistillate flowers; stamens few or numerous, variously united or distinct; ovary 

 usually 3-celled, with 1 or 2 ovules in each cell; fruit mostly a 3-celled capsule, 

 separating at maturity into three 2-valved carpels each containing 2 or mostly 1 large 

 seed. 



KEY TO THE GENERA. 



Flowers involucrate; calyx represented by a minute 

 scale at the base of a filament-like pedicel. 

 Glands of the involucre without petaloid ap- 

 pendages, naked, sometimes with crescent- 

 shaped horns. 

 Stems not terminated by an umbel; stipules 

 gXandlike; involucres cymose-clus- 

 tered, each with a single gland or 

 rarely with 4 glands and fimbriate 



lobes 1. PoiNSETTiA (p. 394). 



Stems terminating in an umbel; stipules 

 none; involucres in open cymes, 

 each with 4 glands and entire or 



toothed lobes 2. TiTHYMALtrs (}:>. 395). 



Glands of the involucres with petaloid append- 

 ages, these sometimes miich reduced. 

 Leaves alternate or scattered, at least below 

 the inflorescence. 

 Perennials; stipules wanting; bracts not 



petaloid; leaves small, narrow 3. Tithymalopsis (p. 396). 



Annuals or biennials; stipules narrow: 

 bracts petaloid; leaves large and 

 broad (those of the inflorescence 



variegated) 4. Dichrophyllum (p. 396). 



Leaves all opposite. 



Leaf blades not oblique at the base; 



leaves mostly rather large 5. Zygophyllidium (p. 397). 



Leaf blades oblique at the base; leaves 



mostly small 6. Chamaesyce (p. 397). 



Flowers not involucrate; calyx of several sepals. 

 Ovules and seeds 2 in each cell. 



Annual; stamens 2; filaments distinct 7. Reverchonia (p. 401). 



Perennial; stamens 3; filaments partly 



united 8. Phyllanthus (p. 401). 



Ovules and seeds solitary in each cell. 



Petals i>resent, at least in the staminate 

 flowers. 

 Flowers in terminal cymes; petals con- 

 spicuous 9. Jatropha (p. 401). 



