30 



SELECTED WESTERN FLORA 



the axil of each bract, each consisting of a more or less 2-celled ovary 

 ■with the rudimentary calyx and 2 long stigmas attached, and en- 

 closed by a bract which becomes enlarged and bladder-like in fruit, 

 these overlapping to form a sort of hop. Slender trees with simple 

 alternate leaves. 



1. O. virginiina, (Miller) Koch. 



Leaves sharply double-serrate and prominently veined, 

 with hard wood and gray, shreddy bark. S. E. Man. 



A small tree 



3. BETULA. BiKCH. 



Sterile flowers 3 to each scale of the catkin, rudiments of a calyx 

 present, bract shield-shaped; fertile flowers 2 or 3 to each bract of 



the catkin, no -rudimentary calyx, 

 bract 3-lobed; ovary naked, becom- 

 ing a winged nutlet. Trees or shrubs 

 with smooth outer bark, separable 

 into sheets. 



1. B. alba, L. White or Canoe Birch. 



Branchlets erect ; leaves ovate, taper- 

 ing to a point, unequally doubly serrate, 

 pale green beneath, slightly hairy on 

 the veins; fruiting catkins generally 

 drooping on slender peduncles. A small 

 to medium-sized graceful tree in our 

 range, but the species varies widely, con- 

 taining many varieties ranging from 

 shrubs to large trees. Across the con- 

 tinent. 



2. B. piimila, L. Swamp Birch. 



Fig. 25.-Betulaalba. young branchlets and lower sides 



of young leaves downy; leaves obovate 

 to orbicular, coarsely dentate, glabrous above when mature but the pubes- 

 cence often persisting beneath ; fruiting catkins erect, about 1 in. long. A 

 shrub sometimes reaching 15 ft. in height. Bogs and wet places, Man.- 

 Alta. (Var. glandulifera, Regel, young branchlets and leaves, glandular- 

 dotted, is also found. The variety is probably the more common western 

 form, but the disti-ictions between it and the type are not always clearly 

 marked.) 



