152 THE AZALEAS OF NORTH AMERICA 



sandy bogs, May 28, 1917, September 22 and 28, 1917 (Nos. 12,830, 

 12,831), March 26 and April 2, 1918, E. J. Palmer (Nos. 13,181, 

 13,265). Hardin County: Silsbee, sandy pine lands, April 25 and 

 September 10, 1916, E. J. Palmer (No. 9568; shrub 4-6 cm. high, 

 flowers pure white, No. 10,689). Without definite locality and date; 

 C. Wright (in Gray Herb.). 



This is the most western species of the eastern group of Rhododendrons and is 

 distributed from northern Arkansas (Newton and Cleburne Counties) to south- 

 eastern Oklahoma and through southeastern Arkansas to southeastern Texas 

 (Houston and Hardin Counties). It is a low shrub growing in moist sandy woods 

 or on the margins of sandy bogs and along streams. 



Rhododendron oblongifolium is most nearly related to R. viscosum and R. serrula- 

 tum, but differs chiefly in the finely villose, sparingly strigose branchlets, the pubes- 

 cent winter-buds, in the larger leaves of thinner texture and usually more or less 

 pubescent, in the larger corolla finely villose and glandular outside and in the usually 

 longer calyx-lobes; the flowers appear earlier, in May or even at the end of April, while 

 R. semdatum flowers in July and August and R. viscosum from the end of May to the 

 beginning of July. Without flowers the pubescent forms of it have some resemblance 

 to R. canescens and have been sometimes confused with that species. It shows 

 considerable variability in some characters, particularly in the pubescence of the 

 leaves, which may be glabrous or more or less pubescent beneath; the extreme forms 

 look very distinct but they are closely connected by numerous intermediates and 

 both forms frequently occur at the same locality and have been distributed by 

 the collectors even under the same number as Bush's No. 5955 1 from Fulton, 

 Arkansas, and Palmer's No. 12,644 from Page, Oklahoma. The upper surface of 

 the leaves also varies from being quite glabrous, except the pubescent midrib, 

 to strigillose and with or without a minute villose pubescence. Sometimes the 

 under side of the leaves is more or less covered with a glaucous bloom, as in part of 

 Palmer's No. 12,644 from Oklahoma and in his 12,062 and part of 12,830 from Texas. 

 The young branchlets may be puberulous all over and sparingly strigose toward 

 the apex or nearly glabrous; the winter-buds are always densely pubescent. The 

 calyx-lobes are sometimes very short and semi-orbicular or ovate, as in Palmer's 

 Nos. 9568, 12,062 and 12,063 from Texas and in his No. 10,583 from Arkansas. The 

 outside of the corolla is usually covered with a thin villose pubescence interspersed 

 with numerous stipitate glands but sometimes, as in Palmer's Nos. 9568 and 12,063, 

 the tube is more densely villose and destitute of glands, which are present only 

 toward the apex of the corolla on the outside of the lobes; in the same numbers the 

 style and the inside of the tube are glabrous. These characters together with the 

 rather dense villose pubescence of the under side of the leaves of No. 12,063 might 

 induce one to make this number the type of a distinct variety, but considering the 

 great variability of the species even in the same locality and the apparent absence 

 of any correlation of the different forms with their geographical distribution, I 

 think it wiser to defer a subdivision of the species into varieties or forms until a 

 careful field study has been made and more copious material is available. 



known growing as far west as Tom Green County, Houston County marking the 

 farthest western limit of the genus in the Eastern States. 



1 The glabrous form of this number looks very distinct, the leaves are broad and 

 generally obovate, quite glabrous except sparingly strigillose on the midrib beneath, 

 even the branchlets are quite glabrous and the specimen, which is in fruit, might be 

 taken for R. arborescens but for the pubescent winter-buds. 



