ASCLEPIADACEAE. 1 95 



Apocynum cannabinum L. Glabrous throughout or sometimes puberulent, 

 pale green; stems erect, branched above, 60-100 cm. high; leaves oblong- 

 elliptic or somewhat lanceolate, cuspidate-acuminate, rounded or cuneate at 

 base, the margin slightly revolute, 2-6 cm. long; petioles 5-8 mm. long; calyx- 

 lobes lanceolate-acuminate, 2-3 times as long as the tube; corolla white, 3-5 

 mm. long, the lobes erect; pods reflexed, linear, tapering at each end, 6-8 cm. 

 long. Two forms of this occur in our limits, the commoner one with flowers 

 3 mm. long, in a small terminal cyme, surrounded by leafy branches {A. suks- 

 dorfii Greene) along streams and in rich fields in the warmer valleys; the other 

 with flowers 5 mm. long in large loose cymes, occurring at Albion, Whitman 

 County. 



Family 73. ASCLEPIADACEAE. 



Herbs with milky juice; leaves entire, opposite, whorled or 

 rarely alternate, without stipules; flowers regular, 5-merous, 

 usually in simple umbels ; corolla gamopetalous, 5-lobed ; stamens 

 attached to the stigma, all the pollen of each anther-cell in one 

 waxy mass; pistils of 2 carpels with two distinct ovaries, buc with 

 a common stigma; fruit a pair of follicles; seed with a coma of 

 silky down; endosperm scant. 



288. ASCLEPIAS. Milkweed. 



Perennial herbs, with copious milky juice; leaves opposite; 

 flowers numerous, in umbels, subtended by a whorl of small 

 bracts, the involucre; calyx and corolla deeply 5 -parted; stamens 

 on the very base of the corolla, monadelphous, short, crowned 

 behind each anther with a hood-like appendage from the cavity 

 of which rises a horn; anthers adherent to the solid stigma; 

 ovaries with short styles; follicles ovate or lanceolate; seeds 

 numerous, each with a long tuft of down, the coma. 



Leaves ovate or oblong, white- tomentose ; follicles warty. A. speciosa. 



Leaves linear or lanceolate, glabrous; follicles smooth. A. mexicana. 



Asclepias speciosa Torr. Stems stout, erect, simple, 80-90 cm. high, 

 thinly white-tomentose throughout; leaves opposite, oblong-ovate, cuspidately 

 acute, rounded at base, 10-15 cm. long, short-petioled ; peduncles stout, longer 

 than the very woolly pedicels; corolla dark-purple, 1 cm. long, the lobes oblong- 

 obtuse; hoods yellowish, spreading, much longer than the stamens and stigma, 

 abruptly narrowed above the dilated base, 12-15 mm. long; horn projecting 

 from near the base; capsules narrowly ovoid, tapering above, white-woolly 

 and with numerous soft spines, 8 mm. long. In moist soil. 



Asclepias mexicana Cav. Glabrous below the inflorescence; stems simple, 

 erect, 40-60 cm. high; leaves mostly in whorls of 3-6, the lowermost opposite, 

 linear or lanceolate, rarely oblong, acute or obtuse, 3-8 cm. long, short-petioled; 

 inflorescence puberulent; peduncles longer than the pedicels; flowers small, 

 5-6 mm. broad, whitish or purplish; hoods ovate, entire, shorter than the 

 stamens, each exceeded by the incurved subulate horn. Valley of the Snake 

 River; Spokane. 



