Rosendahl: observations on betula 457 



This hybrid differs from B. Sandbergi in the more regularly- 

 ovate leaves with less cuneate base, larger number of lateral veins, 

 stouter and more nearly sessile fruiting catkins, larger fruiting 

 bracts and the narrowly winged samaras. In addition, the winter- 

 green flavor of the bark is very characteristic. 



As in the other hybrid, forms occur which resemble one or the 

 other of the parent species more closely. One such collection 

 (Rosendahl 2820) approaches B. litfea in the form, texture and 

 serration of the leaves, but their size averages much less — 2.5-5.5 

 cm. long, 1.4-3.2 cm. wide — and the fruiting catkins are uniformly 

 pedicelled. (This may possibly be identified with Schneider's B. 

 Purpusi var. luteoides, see 1. c, p. 102-107.) 



Whether it belongs to the F^ or the F2 generation, it is difficult 

 to say, but we are inclined to regard it as a second generation hy- 

 brid. An examination of its pollen showed nearly 40 per cent de- 

 fective grains, so there can be little doubt about its hybrid nature. 



Betula pumila x lenta Jack, Garden and Forest, 8: 243. 1895. 

 Betula Jackii Schneider, Lehrb. der Laubholzk. 107. 1906. 



Shrub or small tree with brownish-red bark; young twigs 

 densely pubescent, becoming glabrous or nearly so towards the end 

 of the season, not glandular-dotted, older twigs brownish-red with 

 conspicuous lenticels ; inner bark wath wintergreen flavor; leaves 

 with 5-7 pairs of veins, ovate, rounded at the base, acuminate at 

 the apex, 2.5-5 cm. long, 1.5-3.5 cm. wide, mostly sharply and 

 unevenly serrate, thinly pubescent above, somewhat lighter and 

 densely pubescent beneath, in age becoming nearly glabrous except 

 in the axils of the veins beneath, thick and firm in texture; stam- 

 inate catkins solitary or in two's, terminal or sometimes axillary, 

 4-5 cm. long in anthesis ; pistillate catkins 10-15 mm. long, about 

 4 mm. in diameter ; fruiting catkins ovoid-cylindric, 2-2.7 cm. long, 

 9-12 mm. in diameter, short-stalked or nearly sessile, bracts 5.7-7 

 mm. long, 5-6 mm. wide, at first slightly pubescent on the back and 

 margins, but becoming glabrous in age, lateral lobes spreading, 

 triangular-pointed, as large as the middle lobe ; samaras obovate 

 to obcordate, 3.2-3.4 mm. wide ; nutlet 1.7-1.9 mm. wide, about twice 

 as wide as the wing. 



From the Arnold Arboretum, where it arose spontaneously near 



