722 CALLITRICHACEAE 
ovoid, about 3 mm. long, irregularly 4-angled, ridged and slightly tuberculate. [Ewuphor- 
bia cuphosperma Boiss. ] 
On plains or prairies, South Dakota to Colorado and Mexico. Summer and fall. 
2. Poinsettía dentàta (Michx.) Small. Annual, dull green, mne Stems erect 
or ascending, 2-4 mm. high, somewhat woody below, branched, 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 barbellàta (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 less 
discolored, the base pink, otherwise similar tothe leaves: involucres aggregated in terminal 
clusters, campanulate, 4-5 mm. high, glabrous; lobes incise-toothed : gland solitary, 
oblong or oval, about 2 mm. 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 geniculàta (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, fleshy, 
without appendages: capsules globular, 4-5 mm. long: seeds ovoid, 3-3.5 mm. long, 
reme truncate at the base, irregularly tuberculate-granular. [Huphorbia geniculata 
rtega. 
On hillsides, on both sides of the Rio Grande, Texas and northern Mexico. Also in the West Indies. 
5. Poinsettia Havanénsis ( Willd.) Small. Annual or biennial, glabrous. Stems 
3-10 dm. tall, usually branched, often copiously so, the branches 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, Florida and Central America. Widely distributed in tropical 
America. Spring to fall. 
FAMILY 2. CALLITRICHACEAE Lindl.. WATER STARWORT FAMILY. 
Small mainly aquatic mostly annual caulescent herbs. Leaves opposite: 
blades entire, 3-nerved, 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 flowers. Filaments 
filiform. Anthers 2-celled, the sacs sometimes confluent. Gynoecium of a are 
gle pistil. Ovary 4-celled. Styles united in pairs, slender. Stigmas ety ug 
Ovules solitary in each cavity, pendulous. Fruit leathery, indehiscent, 4-cel zt 
4-lobed. Seeds four. Testa membranous. Endosperm fleshy. Embryo straight, 
axile, terete. 
