168 Rhodora [September 



to passed as B. lutea Michx. f. B. alleghaniensis, based primarily 



upon material from the upper slopes of Mt. Pisgah, western North 



Carolina, distributed by the Biltmore Herbarium as no. 1619, was 



given a broad range: "From Massachusetts to Quebec and northern 



Michigan, south to southern New York, Pennsylvania, and in the 



mountains to Georgia." Subsequently, in his North American Trees 



(1908), Britton made more definite his differentiation of the two 



Yellow Birches by stating the key-characters (p. 247): 



Fruiting scales 4 to 5 mm. long; leaves mostly cordate 



14. B. alleghaniensis. 

 Fruiting scales 8 to 10 mm. long . . . ; leaves rarely cordate 



15. B. lutea. 



On pp. 258 and 259 of the same work, where the two are more 

 fully described and illustrated, B. alleghaniensis is shown with the 

 leaves very definitely not cordate, with scales there described as "4 

 to 6 mm. long" and having "the wedge-shaped part below the lobes 

 very short" and the fruits cuneate-obovate ; while B. lutea, assigned 

 a more northern range, has the scales with prolonged " stalk-like part 

 below the lobes" and the fruits suborbicular. Though recognizing 

 the two extremes indicated by Dr. Britton, various other students of 

 our trees have subsequently been unable to keep them apart as species. 

 Thus, in 1918 Ashe recognized the extreme with short scales as B. 

 lutea, var. alleghaniensis (Britton) Ashe, 1 and more recently I have 

 so designated 2 much of the comon Yellow Birch of Nova Scotia. 

 Subsequently, in an attempt to label properly the material in the 

 Gray Herbarium and the herbarium of the New England Botanical 

 Club, I have carefully studied the specimens, with the result that it 

 seems possible to recognize two strong trends in the scales. The 

 leaves do not show the difference indicated in the key-characters 

 above quoted and, as already noted, Dr. Britton 's own illustration 

 of B. alleghaniensis shows no approach to cordate leaves. Neither 

 does the difference of fruit brought out in his illustrations regularly 

 accompany the differences in the scales. But in general the scales 

 which are only 5-8 mm. long (I have been unable to find any mature 

 scales as short as 4 mm. and the material in the Gray Herbarium of 

 Biltmore Herb. no. 1619, the type-number of B. alleghaniensis, has 

 the scales 7-8 mm. long) and with short (mostly 1-2 mm.) base are 

 of firm or subcoriaceous texture; while the scales of the other extreme, 



x Ashe, Bull. Charleston Mus. xiv. 11 (1918). 

 •Fernald, Rbopoha, xxiii. 257 (1922). 



