88 Miller — Tlic Dogbanes of the District of Columbia. 



Apocynum album Greene. 



■ (PI. IT, Fig. 5.) 



1881. Apocynum cunnahhnnn var. qluherrimvm Ward, Guide to Fldi'a of 

 Washington and Vicinity (Bull. 22. U. S. Nat. Mns.), |i. 97 (not 

 of De Candolle, 1844). 



1897. Jpocynum album. Greene, Pittonia, III, p. 230. December, 1S97. 



1898. Apoci/nnm cannahlnun) glahfrriminn Britton and Brown, 111. Floia, 



N.^ United States, Canada and Brit. Boss., Ill, p. :; (not of De 

 Candolle, 1844). 



7ype locality. —Shore of Potomac Eiver, neai- Chain Bridge, Montgomery 

 County, Maryland. 



Gt'ogroj)Jiic (Ustribiitioii. — The range of Apocyimm album is not well un- 

 derstood. Britton and Brown say, " range apparently nearly of the type, 

 but more abundant northward." I have examined siiecimens from va- 

 rious points in Maryland along the shores of the Potomac River from Old 

 Town to Marshall Hall, also from mouth of Tuccjuan Creek, Lancaster 

 County, Pennsylvania ; Stratford, Connecticut; and Ithaca, New York. 



Zo)ml position. — Probably confined totlie Upper Austral and Transition 

 zones. 



Haliitai. — Beaches and river shores. 



Characters. — Like Apocynum cannabiviim Linnpeus, but of more sU-nder, 

 branching habit, and with smaller, much narrower leaves and essentially 

 white flowers. The lai'gest leaves are about 110 mm. in length by 20-;!0 

 mm. in breadth, those of the upper partof the plant much smaller (about 

 00 X 15). They are oblong-lanceolate in form, those of the upper part of 

 the plant acute at each end, those of lower part of plant rounded at base. 

 All are macronate tipped and wholly glabrous throughout. Petioles 2-3 

 nun. in length. Stems green, very slightly purple tinged, slender and 

 nuich branched, the branching nx)re profuse than in .4. canuabimtjn, but 

 of the same character. Inflorescence in terminal irregular cymes never 

 as large as those commonly met with in A. cannabinum. Calyx lobes 

 about as long as corolla tube or slightly shorter. Corolla about 4 mm. in 

 length, white, often faintly tinged with green, pentagonal, short tubular 

 or faintly canii)anulate, the upright lobes slightly more than half as long 

 as tube, rounded at tips. Pods about 125 mm. in length. Rootstock 

 horizontal, perennial, widely branching. 



Remarks. — Apocynum album is so difterent from A. cannabimim as to re- 

 quire no very close comparison. The peculiar character of its ha))it, 

 leaves, and inflorescence sharply difterentiate it. The white or nearly 

 white flowers, however, are not, taken alone, diagnostic, as forms of .4. 

 cnnnal/nmm frequently occur in which the corolla is equally wliite. 



This i)lant appears to be strictly confined to beaches and river ' bot- 

 toms.' Near Washington it occupies, to the exclusion of other members 

 of the genus, the flats and islands of the Potomac, seldom if ever growing 

 on land that is not flooded at high water. Mr. E. A. Preble has sent me 

 specimens from a small island in the Potomac at Oldtown, Maryland, and 

 Mr. Wm. Palmer has collected it at Marshall Hall. 



