MILKWORT FAMILY 541 



1. P. verticillata L. Stem 0.5-3 dm. high, angled, with numerous spread- 

 ing branches; leaves in 4's or 5's, 1-3 cm. long; racemes spike-like, narrowly 

 conic; flowers greenish or greenish white; wings ovate, about 1 mm. long; keel 

 crested with several thick processes; capsule about 2 mm long Dry soil- 

 Que. Fla. Mex. Wyo. Sask. Plain Submont. Je-S. 



2. P. alba Nutt Stems several from the base, erect or ascending, 1-5 dm. 

 high, angled, simple; leaves 1-2.5 cm. long; racemes spike-like, 4-6 mm. thick; 

 wings oval or obovate, 2-3 mm. long; corolla white; keel with a fimbriate crest; 

 capsule ovoid, 2-3 mm. long. Dry plains: Minn. Kans. Tex. Ariz Colo 

 Mont.; Mex. Plain. Ap-O. 



3: P. Senega L. Stems several from a thick root, erect, 1-5 dm. high, 

 simple; leaves numerous, lanceolate to lance-elliptic or (in var. latifolia) ovate- 

 lanceolate or ovate, scabrous on the margin; racemes spike-like, 2-6 cm. long; 

 wings orbicular-ovate, 2-3 mm. long; corolla greenish white, 3-4 mm. long; keel 

 crested with thick processes; capsule flat, broader than long. Dry soil' N B 

 N.C. Ark. (Black Hills) S.D. Alta. Submont. My-Jl. 



4. P. subspinosa S. Wats. Spinescent undershrub, intricately branched, 

 puberulent; leaves lance-oblong to elliptic or spatulate, 1-2 cm. long, firm; 

 inflorescence a few-flowered raceme; wings elliptic-oblong, acutish, as well as 

 tips of the lateral petals rose-colored; keel yellow, with a blunt beak; capsule 

 obovate, retuse, veiny, glabrous. Foot-hills: Colo. Ariz. Nev. Son. Sub- 

 mont. My-Jl. 



6. P. acanthoclada A. Gray. Spinescent shrub, with white or yellowish 

 bark, intricately branched; leaves 6-12 mm. long; oblanceqlate or spatulate; 

 racemes few-flowered, with a stout peduncle produced into a spine; flowers yellow- 

 ish white, or the petals tipped with purplish; wings obovate; keel with a very short 

 blunt, often obsolete, beak; fruit oblong-ovate, 5 mm. long, deeply notched. 

 Arid regions: Colo. Ariz. Nev. Son. Je. 



FAMILY 74. EUPHORBIACEAE. SPURGE FAMILY. 



Monoecious or dioecious herbs (all ours), or shrubs or trees, often with 

 milky sap, and alternate, opposite, or verticillate simple leaves. Flowers 

 with or without petals, sometimes much reduced and subtended by a calyx- 

 like involucre. Stamens few or many; filaments united or distinct. Ovary 

 usually 3-celled. Styles as many as the cells of the ovary, simple, divided, 

 or many-cleft. Capsule separating at maturity into three 2-valved carpels. 



Flowers not in involucres; calyx of several sepals. 



Corolla present in either the staminate or pistillate flowers, or in both. 



Stamens 5 or 6; filaments distinct. 1. CROTON. 



Stamens 10; filaments monadelphous. 2. DITAXIS. 



Corolla wanting. 3. TKAGIA. 



Flowers in involucres; calyx represented by a minute scale on the filament-like pedicels. 

 Glands of the involucres with petal-like appendages, these however sometimes much 



reduced. 

 Leaves all opposite. 



Leaf-blades oblique at the base, inequilateral; glands 4. 4. CHAMAESYCB. 

 Leaf-blades equilateral, not oblique at the base; glands 5. 



5. ZYGOPHYLLIDIUM. 

 Leaves alternate or scattered, at least below the inflorescence; annuals or bien- 



enials; bracts petal-like. 6. LEPADENIA. 



Glands of the involucres without petal-like appendages, entirely naked, sometimes 



with crescent-shaped horns. 

 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 conglomerate 

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



8. POINSETTIA. 



1. CROTON L. CROTON. 



Herbs (ours) or shrubs, monoecious or rarely dioecious, heavy-scented, stel- 

 late-pubescent or scaly, sometimes more or less glandular. Leaves mostly alter- 

 nate, entire, toothed or lobed. Flowers in axillary or terminal clusters. Stam- 



