SPURGE FAMILY 547 



7. T. arkansanus (Engelm. & Gray) Kl. & Garke. Annual or biennial; stem 

 slender, 2-5 dm. high, branched; leaves few, cuneate or spatulate, acute, serru- 

 late, 1-3 cm. long, 5-10 mm. wide; bracts broadly triangular-ovate to oblong, 

 mucronate, serrulate, the larger 1 cm. wide, 1-2 cm. long; involucres 1 mm. 

 high; glands transversely elliptic, yellow, less than 1 mm. wide; capsule depressed 

 globose, verrucose, 2.5-3 mm. wide; seeds ovoid-lenticular, browm or purplish, 

 wrinkled, reticulate, nearly 1.5 mm. long. E. arkansana Engelm. & Gray. 

 Plains and sandy places: N.D. — Mo. — Ala. — Tex. — Ariz.— Wyo.; Mex. Plain. 

 Ap-Je. 



8. T. missouriensis (Norton) Small. Annual or biennial, olive-green; 

 stem 3-6 dm. high, stout; stem-leaves spatulate, 2-3.5 cm. long, obtuse, serrate 

 to below the middle; bracts ovate, inequilateral, acute, serrate; involucres 

 less than 2 mm. high; glands transversely oblong; capsules 3-3.5 mm. wide, 

 bearing elongated warts; seeds ovoid, distinctly and regularly reticulate, purpUsh- 

 brown. E. arkansana missouriensis 'Norton. Dry plains: Minn. — Kans. — N.M. 

 —Wash. Plain. My-Jl. 



8. POINSETTIA Graham. Spurge. 



Annual or perennial herbs, or shrubby plants, with green or partially colored 

 foliage. Leaves alternate below, opposite above. Stipules gland-like. Invo- 

 lucres in axillary or terminal cymes, or solitary; lobes fimbriate. Glands fleshy, 

 solitary, or rarely 3 or 4, without appendages. Capsule 3-lobed, lobes rounded. 

 Seeds narrowed upwards, tuberculate. 



Gland or glands of the involucre stalked; bracts and upper leaves slightly if at all dis- 

 colored. 

 Seeds not prominently tubercled; glands of the involucre 3-4; leaf-blades linear or 

 Unear-lanceolate. 1. P. cuphusperma. 



Seeds prominently tubercled; gland of the involucre solitary; leaf-blades ovate to 

 lanceolate (hnear-lanceolate only in one variety). 2. P. dentata. 



Gland of the involucre sessile or nearly so ; bracts and upper leaves discolored at the base ; 

 leaf-blades very variable, the upper usually flddle-shaped. 3. P. heterophylla. 



1. P. cuphusperma (Boiss.) Small. Simple annual; stem 2-4 dm. high, 

 more or less pubescent, especially upwards, erect; leaf -blades 2-8.5 cm. long, 

 entire or denticulate; involucres crowded at the ends of the branches, almost 4 

 mm. long; capsule 5 mm. in diameter; seeds narrowly ovoid, 3 mm. long, ir- 

 regularly 4-angled, ridged and slightly tuberculate. E. cuphusperma Boiss. 

 Plains and prairies: S.D. — Colo. — Ariz. — Tex. — Mex. Son. — Submont. Au- 

 S. 



2. P. dentata (Michx.) Small. Pubescent annual; stem erect or ascending, 

 2-4 dm. high, somewhat woody at the base, branched; leaf-blades from ovate to 

 nearl}^ linear or orbicular-oblong, 1-9 cm. long, coarsely dentate; involucres 

 about 3 mm. long; capsule glabrous, 4-5 mm. in diameter; seeds ovoid-globose, 

 ash-colored, inconspicuously 4-angled. E. dentata Michx. Dry soil: S.D. — 

 Pa. — La. — IMex. Plain — Submont. Je-S. 



3. P. heterophylla (L.) Small. Bright green annual or biennial, pubescent 

 or nearly glabrous; stem erect, 3-10 dm. high, woody below; leaf-blades linear 

 to orbicular, the lower ones often entire, the upper undulate, sinuate, or dentate, 

 the uppermost often fiddle-shaped and like the bracts blotched with red; invo- 

 lucres 3 mm. long, with 5 ovate or oblong laciniate lobes, one sinus bearing a 

 sessile gland; capsule glabrous or minutely pubescent, 6 mm. broad; seeds oblong- 

 ovoid, 3-4 mm. long, transversely wTinkled and tuberculate. E. heterophylla L. 

 Sandy soil: III. — Fla. — Tex. — Mont.; INIex. and trop. Am. Plain. Ja-D. 



Family 75. CALLITRICHACEAE. Water Starwort Family. 



Small aquatic caulescent annuals or perennials, with opposite, entire 

 leaves, often crowded towards the end of the branches. Flowers inconspic- 

 uous, solitary in the axils of the leaves, polygamous. Calyx wanting. 

 Corolla none. Stamens solitary; anthers 2-celled; cells sometimes con- 



