Betula Betulaceae 375 



Bark of trunk white, peeling in very thin strips; mature fruiting catkins drooping 

 or spreading; wings of fruit wider than the nut. 

 Trunk of tree with a darkened triangular area at the base of lateral branches; 



leaves long-acuminate, lustrous above; staminate catkins usually solitary 



2. B. populifolia. 



Trunk of tree without a darkened area at the base of lateral branches; leaves 



ovate, not lustrous above; staminate catkins usually 2 or 3. . .3. B. papyrifera. 



Bark of trunk (tree or shrub) dark or reddish brown, not peeling off in thin strips 



(flaking off in thick plates in B. nigra); fruiting catkins erect or nearly so; 



wings of fruit narrower than the nut. 



Bark of large specimens peeling or flaking; leaves triangular-ovate, widest below 



the middle, mostly with 7-9 pairs of prominent veins; bracts of mature fruiting 



catkins 6-10 mm long, densely pubescent; trees 4. B. nigra. 



Bark tight; leaves oblong-ovate, elliptic, obovate, rarely ovate, mostly with 3-6 



(7) pairs of prominent veins; bracts of mature fruiting catkins 4-7 mm long, 



glabrous except the ciliate margins; shrubs or shrublike trees. 



Blades generally with 3 or 4 pairs of distinct veins, 2-4 cm long on fruiting 



branchlets, obovate, rounded at the apex, rarely short-acute, cuneate at 



the base. 



Leaves not glandular 5. B. pumila. 



Leaves more or less glandular, glands usually plentiful on both sides 



5a. B. pumila var. glandulifera. 



Blades generally with 6 or 7 pairs of distinct veins, mostly 5-6 cm long on fruiting 

 branchlets, oblong-ovate, elliptic or rarely ovate, acute at the apex, mostly 

 rounded or subcordate at the base 6. X B. Ptirpusii. 



1. Betula lutea Michx. f. (Betula alleghaniensis Britt.) Yellow Birch. 

 After a careful study of my specimens, I believe they all belong to the 

 variety rather than to the species. Fernald (Rhodora 24: 170. 1922) 

 refers to two specimens of the species from Indiana. 



Newf. to Man., southw. to Del., 111., and Minn, and in the mts. of N. C. 

 and W. Va. 



la. Betula lutea var. macrolepis Fern. (Rhodora 24: 170. 1922.) 

 Yellow Birch. Map 771. This tree is found locally in the northern part 

 of the state and on the sides of two deep, rocky ravines about a mile 

 east of Taswell in Crawford County. In northern Indiana it apparently 

 is one of the chief species in the succession after tamarack and is asso- 

 ciated with white elm, red maple, black ash, and silver maple. All 

 of my northern specimens have a dark bark and I believe they all belong 

 to the dark bark form recently described by Fassett (Rhodora 34: 95. 

 1932) as Betula lutea Michx. f. forma fallax Fassett. 



N. B. to Wis., southw. to Tenn. and 111. 



2. Betula populifolia Marsh. Gray Birch. Map 772. The few trees 

 of this species found in Indiana are the remnants of a relic colony because 

 the nearest location of this species is three to four hundred miles to the 

 northeast. In 1911 I found a few trees in a dying condition on the border 

 of Fish-trap Lake near La Porte in La Porte County. I have a specimen 

 collected by Blatchley in Lake County (Ind. Geol. Rept. 22: 100. 1898). 

 He says: "Sand ridges west of Miller's; scarce." This species has been 



