LYTHRACEAE. 167 



Mentzelia integrifolia (Wats.) Rydb. Annual, puberulent throughout; 

 stem white, erect, rarely decumbent, more or less branched, 10-40 cm. high; 

 leaves oblong or lanceolate or the upper ovate, entire or sinuately pinnatifid, 

 2-6 cm. long, sessile; flowers yellow, sessile or nearly so, in leafy cymes, 6-10 

 mm. broad; calyx-lobes deltoid-lanceolate, shorter than the petals; capsule 

 linear, 2-3 mm. long; seeds nearly cubical, smooth, grooved on the angles. 

 Dry soil, Wawawai and Cedar Mountains, Idaho. 



Family 61. CACTACEAE. Cactus Family. 



Fleshy and thickened plants; stems flattened, terete, ridged 

 or tubercled, continuous or jointed, leafless or with small leaves, 

 generally spiny ; spines from cushions of minute bristles ; flowers 

 solitary, sessile, perfect, regular, showy; sepals and petals 

 numerous, in several rows, the bases adherent to the ovary; 

 stamens numerous, on the calyx-tube; style 1; ovary 1-celled, 

 with several parietal placentae ; ovules numerous ; fruit a 1-celled 

 berry; endosperm scanty or copious. 



236. OPUNTIA Prickly Pear. 



Jointed, much-branched plants; leaves small, terete, subulate, 

 early deciduous, on young branches; flowers usually lateral, 

 large ; calyx-tube not prolonged beyond the ovary ; lobes numer- 

 ous, spreading; petals numerous, slightly united; stamens very 

 numerous, in several rows; fruit a berry, often prickly. 



Opuntia polyacantha Haw. Prostrate, frequently in large tufts; joints of 

 the stem flattened, orbicular or oblong, 5-12 cm. long, pale-green; leaves 

 minute, 3-4 mm. long; cushions pale bristly; spines 4-8, whitish, usually 

 red-tipped, 5-20 mm. long, mostly deflexed; flowers yellow, 4-S cm. broad; 

 fruit ovate, dry, 2.5 cm. long, with a shallow saucer-like apex. Rocky and 

 sandy places, banks of Snake River. 



Family 62. LYTHRACEAE. 



Herbs; leaves mostly opposite and entire, with no stipules; 

 flowers axillary or whorled, perfect; calyx enclosing but free from 

 the ovary; petals 4-7, as many as the calyx-teeth, perigynous, or 

 none ; stamens 4-14, on the calyx ; style 1 ; ovary 2-4-celled ; 

 ovules numerous, rarely few; fruit a membranous capsule; endo- 

 sperm none. 



Flowers mostly more than one in the axils; capsule burst- 

 ing irregularly. 237. Ammannia, 168. 



Flowers mostly solitary in the axils; capsule septicidally 



dehiscent. 238. Rotala, 168. 



