762 Apocynaceae Apocynum 



6684. APOCYNUM L. Indian Hemp. Dogbane 



[Woodson. Studies in Apocynaceae. I. Ann. Missouri Bot. Gard. 17: 

 1-213. 1930.] 



It is evident from the various treatments by authors of the species of 

 Apocynum that occur in our area that they are not well understood. Since 

 Woodson has written the latest monograph and made the most intensive 

 study of our species, I have followed his monograph although I am con- 

 vinced that additional field studies will alter our present treatment of 

 them. 



Stem leaves drooping or spreading; corollas at least twice as long as the calyx lobes, 

 mostly 3-6 mm long in dried specimens, campanulate, with recurved, spreading or 

 rarely erect lobes, pink, pinkish, white striped with pink, or rarely colorless (in 

 2a and 2b) ; stems unevenly dichotomously branched, spreading at maturity or 

 somewhat erect if crowded by vegetation of equal height; inflorescence usually 

 above the foliage; coma of seeds tawny, mostly 1.5-2 cm long. 

 Corollas at least three times as long as the calyx lobes, mostly 4-6 mm long in dried 

 specimens, pink, pinkish or white striped with pink, the lobes recurved, strongly 

 fragrant; stems conspicuously dichotomously branched; stem leaves and some- 

 times those of the branches drooping; follicles 6-15 cm long, straight or nearly 



so; seed about 2 mm long 1. A. androsaemifolium. 



Corollas about twice as long as the calyx lobes, mostly 3-4 mm long in dried speci- 

 mens, faintly pink or colorless in 2a and 2b, the lobes generally spreading; stems 

 more or less dichotomously branched; stem leaves spreading, rarely ascending; 

 follicles 7-15 cm long, straight, divergent, or somewhat falcate; seed about 4 mm 

 long. 

 Plants not glabrous throughout. 



Calyx glabrous without, the lobes pinkish 2. A. medium. 



Calyx hirtellous without, the lobes colorless 2a. A. medium var. samiense. 



Plants glabrous throughout; calyx lobes colorless. .2b. A. medium var. leuconeuron. 

 Stem leaves ascending; corollas less than twice as long as the calyx lobes, usually 2.5-4 

 mm long in dried specimens, white or greenish white, tubular, sometimes the tube 

 very short, the lobes erect; the cymose inflorescences conspicuously overtopped by 

 sterile branches. 

 Stem leaves evidently petiolate, narrowed to the base, or the very lowest sessile and 

 obtuse at the base; follicles relatively long and usually falcate, 12-20 cm long; 

 coma of seed 20-30 mm long. 

 Plant pubescent, at least the lower surface of the leaves. 



Plant glabrous except the lower surface of the leaves 3. A. cannabinum. 



Plant pubescent on both surfaces of the leaves and in the inflorescence. 



3a. A. cannabinum var. pubescens. 



Plant entirely glabrous 3b. A. cannabinum var. glaberrimum. 



Stem leaves sessile or subsessile, cordate or subcordate at the base and often clasp- 

 ing, oblong to lanceolate; follicles relatively short and straight, 4-10 cm long; 

 coma of seed white, 8-20 mm long. 



Leaves glabrous on both surfaces 4. A. sibiricum. 



Leaves pubescent on the lower surface, at least along the veins 



4a. A. sibimcum var. Farwellii. 



1. Apocynum androsaemifolium L. SPREADING DOGBANE. Map 1634. 

 More or less infrequent in rather sandy or gravelly soil throughout the 

 northern counties along roadsides and in open woodland, where it is 

 associated with black and white oak. In southern Indiana it has a similar 

 habitat but becomes rare to very rare. 



Throughout temperate N. A. 



