722 CALLLTRICHACEAE 



ovoid, about 3 mm. long, irregularly 4-angled, ridgedand slightly tuberculate. [Euphor- 

 bia cuphosperma Boiss. ] 



On plains or prairies, South Dakota to Colorado and Mexico. Summer and fall. 



2. Poinsettla dentata,(Michx.) Small. Annual, dull green, pubescent. Stems erect 

 or ascending, 2-4 mm. high, somewhat woody below, branciied, the branches mostly as- 

 cending : leaves opposite, or the lowest alternate ; blades varying from ovate to nearly lin- 

 ear or orbicular-oblong, 1-9 cm. long, coarsely dentate, narrowed into slender petioles, the 

 nerves prominent beneath : involucres oblong-campanulate, about 3 mm. long, 3-5-lobed, 

 bearing 1-4 yellowish short-stalked glands without appendages : capsules glabrous, 4-5 mm. 

 in diameter : seeds ovoid-globose, ash-colored, irregularly tuberculate, inconspicuously 4- 

 angled. [Euphorbia dentata Michx. ] 



In dry or moist soil, Pennsylvania to South Dakota, Louisiana and Mexico. Summer and fall. 



3. Poinsettia barbellata (Engelm. ) Small. Annual or biennial, glabrous or nearly 

 so. Stems erect or ascending, 3-7 dm. tall, somewhat branched : leaves alternate ; blades 

 various, linear to oblong, 5-15 cm. long, acuminate, remotely serrate with often bristle- 

 tipped teeth, or lobed, sparingly bearded at the base, short-petioled : bracts more or le&s 

 discolored, the base pink, otherwise similar to the leaves : involucres aggregated in terminal 

 clusters, campanulate, 4-5 mm. high, glabrous ; lobes incise-toothed : gland solitary, 

 oblong or oval, about 2 ram. broad, sessile : capsules subglobose, 3-3.5 mm. long : seeds 

 oblong, fully 2 mm. long. [Euphorbia barbellata Engelm.} 



On plains and prairies, Texas. Spring to fall. 



4. Poinsettia geniculata (Ortega) Small. Annual. Stems erect or ascending, 3-9 

 <dm. tall, forking above, corymbose : leaves alternate below, opposite above ; blades oblong 

 •or ovate, 4-9 cm. long, acute or acuminate above, entire or obsoletely dentate, acuminate 

 at the base, short-petioled : involucres in dense cymes, cylindric-turbinate, 3-3.5 mm. high, 

 short-peduncled ; lobes dentate-fimbriate : glands solitary, somewhat stalked, iiesliy, 

 without appendages : capsules globular, 4-5 mm. long : seeds ovoid, 3-3.5 mm. long, 

 blackish, truncate at the base, irregularly tuberculate-granular. [Euphorbia geniculata 

 Ortega.] 



On hillsides, on both sides of the Rio Grande, Texas and northern Mexico. Also in the West Indies. 



5. Poinsettia Havan^nsis (Willd. ) Small. Annual or biennial, glabrous. Stems 

 3-10 dm. tall, usually branched, often copiously so, the Ijranches more or less spreading : 

 leaves alternate ; blades narrowly linear or sometimes slightly widened near the base, 4-15 

 cm. long, entire, often somewhat revolute : bracts similar to the leaves but with a purple 

 red or scarlet blotch at the base : involucres clustered, 2-2.5 mm. high, short-peduncled, 

 with 5 ovate sparingly laciniate lobes, one sinus bearing a sessile unappendaged gland : 

 capsules glabrous, strongly 3-lobed, 5-6 mm. broad : seeds broadly oblong, 2-5 mm. long, 

 black, very rough. [Euphorbia graminifolia Michx., not Vill. E. Havanensis Willd.] 



In dry or sandy soil, Georgia and Florida to Texas. Also in tropical America. 



6. Poinsettia heterophylla (L. ) Small. Annual or biennial, bright green, pubes- 

 cent or nearly glabrous. Stems mostly erect, 3-10 dm. tall, woody below, the branches 

 ascending, or the lower spreading, leafy at the ends : leaves alternate ; blades very variable, 

 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 : involucres clustered 

 at the ends of the branches, 3 mm. long, about equalling the peduncles, with 5 ovate or 

 oblong laciniate lobes, one sinus bearing a sessile gland without an appendage : capsules 

 glabrous or minutely pubescent, 6 mm. broad : seeds oblong-ovoid, 3-4 mm. long, trans- 

 versely wrinkled and tuberculate. [Euphorbia heterophylla L. ] 



In sandy soil, Illinois to Montana, riorida and Central America. Widely distributed in tropical 

 America. Spring to fall. 



Family 2. CALLITRICHACEAE Liudl. Water Star wort Family. 



Small mainly aquatic mostly annual caulescent herbs. Leaves opposite : 

 blades entire, 3-nei'ved, often imbricated at the end of the stem. Flowers mi- 

 nute, polygamous, solitary in the axils. Calyx wanting. Corolla wanting. 

 Androecium of a solitary stamen, 2-bracted in the staminate fiow'ers. Filaments 

 filiform. Anthers 2-celIed, the sacs sometimes confluent. Gynoecium of a sin- 

 gle pistil. Ovary 4-celled. Styles united in pairs, slender. Stigmas acute. 

 Ovules solitary in each cavity, pendulous. Fruit leathery, indehiscent, 4-celled, 

 4-lobed. Seeds four. Testa membranous. Endosperm fleshy. Embryo straight, 

 axile, terete. 



