narrowly 2-lobed connective; ovary apocarpous, containing numerous ovules, 

 surrounded at the base by 5 distinct ovoid nectaries; stigma usually virtually sessile, 

 variable in shape but essentially ovoid-fusiform; follicles usually 2, separate or 

 somewhat agglutinated at the tips, slender, terete; seeds numerous, truncate, 

 comose. 



About 7 species in North America and 70 elsewhere in temperate and tropical 

 regions. The separation of species in this extremely complex genus is not too 

 satisfactory. 



1. Leaves noticeably petiolate or only the very lowest sessile, narrowed to broadly 

 rounded at the base, pubescent to glabrous; bracts of inflorescence 

 scarious and aristate 1. A. cannahimim. 



1. Leaves sessile or nearly so, the lowest cordate at base and usually clasping 

 the stem, always glabrous; bracts of inflorescence more or less 

 foliaceous and laminate 2. A. sibiricum. 



1. Apocynum cannabinum L. Indian hemp. Fig. 633A. 



Plant glabrous to variously pubescent; stems erect or ascending to 1 m. tall, 

 glabrous, with ascending branches; leaves petiolate or the lowermost sometimes 

 subsessile, ascending or only slightly spreading, ovate to oblong-elliptic or lanceo- 

 late, rounded to acute and usually apiculate at apex, narrowly cuneate to some- 

 what rounded at base, to 14 cm. long and 7 cm. broad, glabrous above, glabrous 

 to more or less densely pilosulous or tomentulose beneath; calyx lobes lanceolate 

 to ovate-lanceolate, 3-4 mm. long, glabrous; corolla cylindric to urceolate, 3-6 

 mm. long, white to greenish, the lobes erect or only slightly spreading; follicles 

 12-20 cm. long, glabrous, pendulous at maturity. 



Usually in wet or moist sandy or clayey soil in ditches and along streams and 

 rivers, in marshy areas, about ponds, occasionally in fields and open woodlands 

 in e., cen. and n.-cen. Tex. and Okla. (Osage, Ottawa and LeFlore cos.), Apr.— 

 Aug.; throughout the U.S. and s. Can. 



Those plants that are entirely glabrous throughout are segregated as var. 

 glaberrimum A. DC., while those plants that are more or less tomentulose 

 throughout are segregated as var. puhescens (R.Br.) A. DC. 



2. Apocynum sibiricum Jacq. Prairie dogbane. 



Stems erect or somewhat ascending to 7 dm. tall, glabrous throughout, with 

 ascending branches; leaves sessile or subsessile (especially on the main stem) and 

 often with a cordate-clasping base, those on the upper branches frequently shortly 

 petiolate, ascending or slightly spreading, oblong or oblong-lanceolate to oval 

 or rarely linear to linear-lanceolate, to 14 cm. long and 45 mm. wide, obtuse to 

 rounded or cordate at the base; inflorescence usually dense, the bracts usually 

 conspicuous and more or less herbaceous; calyx lobes lanceolate, 2-4 mm. long; 

 corolla urceolate to shortly cylindric, about as long as broad, 3-5 mm. long, white 

 to yellow or greenish, glabrous externally, the lobes erect or slightly spreading; 

 follicles 4-10 cm. long, glabrous, pendulous at maturity. A. hypericifolium Ait., 

 A. Suksdorfii Greene. 



Usually in sandy soil along creeks and on dunes, in marshes about lakes, 

 seepage along streams and about springs and in arroyos and gullies of badlands in 

 n.-cen. Tex., the Edwards Plateau, Plains Country and Trans-Pecos, Okla. (Alfalfa 

 Co.) and N. M. (Eddy, Dona Ana and Guadalupe cos.), Apr.-Sept.; throughout 

 most of N.A. 



Those plants with the main stem leaves ovate to oval-oblong and deeply cor- 

 date and clasping at the base are segregated as var. cordigerum (Greene) Fern., 

 while those plants with very narrow leaves and corolla longer than broad are 

 segregated as var. salignwn (Greene) Fern. [A. angnstifolium Woot., A. Suksdorfii 

 var.angustifolium (Woot.) Woods.] 



1337 



