ENUMERATION OF THE SPECIES 159 



West Virginia, western North Carolina and southeastern Tennessee and south- 

 western South Carolina (Oconee County). It also has been reported from north- 

 eastern Ohio. 1 It forms a densely-branched shrub from 1 to 5 meters tall and grows 

 almost exclusively in swamps together with other swamp-loving shrubs and trees; 

 it is rather common in the swamps of the coastal plain from southwestern Maine 

 to South Carolina, but it also is found in swamps on the higher mountains. 



Rhododendron viscosum is a very variable species, but it is never pubescent except 

 in one rare variety and in this respect differs from the otherwise very closely related 

 R. serrulatum from which it is often difficult to distinguish. With the latter 

 species and with R. arborescens, R. oblongifolium and R. atlanticum, it forms 

 a group of very closely connected species which have been frequently confused and 

 are sometimes not easily distinguished from each other. The most distinct and 

 least variable is R. arborescens, which differs from all these related species in the 

 glabrous branchlets, glabrous leaves and usually glabrous style; R. atlanticum 

 differs in its early flowers appearing before or with the leaves, in the absence of 

 the villose pubescence of the corolla and in its low stature and stoloniferous habit; 

 R. oblongifolium differs chiefly in its usually more or less pubescent, larger and 

 narrower, acute or sometimes almost acuminate leaves, in the usually larger calyx- 

 lobes, the larger more villose and less glandular corolla and in the always pubescent 

 winter-buds. The most closely related species is R. serrulatum which might be 

 considered only a southern variety of R. viscosum and in fact was not separated 

 at all from the latter species until recently; it may be chiefly distinguished by the 

 more chartaceous, setosely serrulate, somewhat reticulate, often pubescent leaves 

 never glaucous beneath, the more numerous always distinctly mucronate, often 

 aristate scales of its floral winter-buds, the longer and slenderer corolla-tube 

 about twice as long as the lobes and the bright red-brown branchlets usually 

 densely strigose toward the apex. Rhododendron viscosum varies in the pubescence 

 of its winter-buds, in the amount and character of the strigose or hirsute pubes- 

 cence on the branchlets and leaves, in the color and shape of the leaves which may 

 be bright green or more or less glaucous and vary from obovate to oblong-lance- 

 olate, in the size and color of the flowers which may be almost pure white or more 

 or less pink, rarely deep pink. Sometimes it has the low stoloniferous habit of 

 R. atlanticum; e. g. I. Tidestrom's No. 7080, from between Berwyn and Lanham, 

 Maryland, June 8, 1914, L. F. Ward's specimen from Terra Cotta Swamp, 

 Washington, D. C, June 13, 1880 (Nat. Herb. No. 14,480), E. S. Steele's specimen 

 from Hyattsville, Maryland, May 31, 1915 (Nat. Herb. No. 835,633) and Witmer 

 Stone's No. 571, from Tyndalls Mill, south of Manning, South Carolina, May 5, 

 1917; also P. C. Standley's No. 11,547 from Hyattsville Swamp, May 27, 1915, 



1 Newberry, Cat. PI. Ohio, 24 (1860). — Kellerman, Cat. Ohio PI. 129 (in Rep. 

 Geol. Surv. Ohio, VII. pt. 2) (1893). — Schaffner, Cat. Ohio Vase. PI. 204 (in Ohio 

 Biol. Surv. I.) (1914). — Rhododendron viscosum was first reported from Ohio by 

 Newberry in 1860 without definite locality except "East." Kellerman in 1893 

 quotes it from Beardslee's Catalogue of 1874, where it is recorded from near Paines- 

 ville. Schaffner in 1914 gives Ashtabula County as the only locality for the species. 

 Among the Azaleas from the herbarium of the Ohio State University received 

 through the kindness of Professor J. H. Schaffner I found only one specimen 

 labeled Azalea viscosa L., Pymatuming Swamp, Ashtabula County, August 11, 1900, 

 C. A. Davis, A. Dachnowski, F. Detmers. This specimen has neither flowers nor 

 fruits and is apparently some form of R. roseum; it is certainly not R. viscosum. 

 Beardslee's record is probably based on a similar form; Professor Schaffner writes 

 me that there are a few of Beardslee's specimens in the herbarium of the Ohio 

 State University, but none labeled Azalea viscosa, and that Newberry's Catalogue 

 was not based on specimens that could be verified. 



