The Dogbanes of the District of Columbia. 87 



tinged with yellow, often densely pubescent, and seldom if ever without 

 trace of pubescence, at least on the veins; petioles 3-7 mm. in length, 

 slender above, shorter and robust below, pubescent or glabrous on under 

 side; inflorescence in strictly terminal cymes, the larger of which are dis 

 tinctly flat topped, the central cyme always developing first, and gener 

 ally the largest; cymes composed of very many erect flowers and gener 

 ally exceeded by the leaves ; pedicels 1-4 mm. in length, subulate-bracted 

 at base, glabrous or pubescent ; caly.i- glabrous or pubescent, its segments 

 very variable in form, but usually about equal to corolla tube in length, 

 or slightly shorter, the tips appressed or widely spreading; corolla vary 

 ing in color from white to dull green, and in length from 3 mm. to 4.5 

 mm., generally glabrous, but often pubescent, pentagonal, tubular or 

 slightly campanulate ; corolla segments equal to or shorter than tube, 

 rounded or bluntly pointed at tips, erect or very slightly spreading, the 

 margins usually slightly revolute; pods drooping, 130-200 mm. in length. 

 Remarks. Apocynum cannabinum is a highly polymorphic species, much 

 in need of critical study. It is readily distinguished, among the species 

 known to occur in the eastern United States, by its robust, upright habit, 

 large, short-petioled leaves, and small, green, greenish, whitish, or white 

 flowers, with erect corolla lobes. Within these limits, however, variation 

 is so great as to suggest the existence of numerous partly or perhaps com 

 pletely segregated forms. Of those that occur in the District of Colum 

 bia, the most strongly marked is the A . pubescens of R. Brown. The whole 

 plant (or the upper part at least) is densely velvety pubescent, and the 

 upper leaves are unusually short, broad, and closely set. Flowers green 

 ish or white. This is probably not the A . pubescens of Britton and Brown. 

 Glabrate and narrow-leaved forms occur, and others of unusually slender 

 habit ; but I have seen none that bridge the gap between A. cannabinum 

 and either of the following species. 



Apocynum nemorale sp. nov. 



Type No. 340,397, United States National Herbarium, collected at road 

 side in woods near end of Chain Bridge, Fairfax County, Virginia, July 

 14, 1899, by Win. Palmer. 



Geographic distribution. This species is now known only from the type 

 locality and the Virginia shore of the Potomac River at Great Falls. 



Zonal position. Probably confined to the Upper Austral and Transition 

 zones. 



Habitat. Open woods. 



Characters. Like Apocynum cannabinum Linnaeus, but with relatively 

 few, spreading or drooping, leaves on slender petioles (usually 10-15 mm. 

 in length) two or three times as long as flowers ; corolla glabrous, greenish. 



Remarks. I should hesitate to separate this plant from Apocynum can 

 nabinum were not its characters, trivial though they appear on paper, 

 striking and constant in specimens, especially those living or freshly col 

 lected. Furthermore, while A. cannabinum occasionally occurs in open 

 woods, together with A. nemorale, it never, so far as known, shows any 

 tendency to assume the characters of the latter. 



21 Bun,. Sue. WASH., VOL. XIII, 1899 



