BIRCH 



compressed, two-celled, crowned with two slender styles ; 

 the ovule is solitary. 



The ripened pistillate ament is called a strobile and bears 

 tiny winged nuts, packed in the protecting curve of each 

 brown and woody scale. These nuts are pale chestnut brown, 

 compressed, crowned by the persistent stigmas. The seed 

 fills the cavity of the nut. The 

 cotyledons are flat and fleshy. All 

 the species are easily grown from 

 seed. 



Michaux arranged the birches 



into tWO groups One, including Rear View of a Staminate Scale and 



trees whose pistillate aments are ^i^S STl^ 

 sessile and erect : the Black, the Enlarged. 

 Yellow and the Red ; the other, 



those whose pistillate aments are stalked and pendulous : 

 the Canoe, the White and the common Betula alba of Europe. 

 Remains of the group appear in the cretaceous rocks of 

 Dakota, and during the tertiary period the genus existed 

 throughout the northern central plateau of North America 

 and at the same time abounded in Europe. 



WHITE BIRCH. GRAY BIRCH. ASPEN-LEAVED BIRCH 



Betula populifblia. 



Least common of the birches ; found on dry, gravelly, barren mar- 

 gins of swamps and ponds. Short-lived, twenty to thirty feet high. 

 Grows very rapidly. Ranges from Nova Scotia and lower St. Law- 

 rence River southward mostly in the coast region to Delaware, and 

 westward through northern New England and New York to southern 

 shore of Lake Ontario. Leaves tremulous. 



Bark. Chalky white or gray white, usually firm but easily sep- 

 erable into thin plates ; dark triangular markings scattered over the 

 trunk and especially below the branches. At the base of large trees 

 nearly black and broken irregularly by shallow fissures. Branchlets 

 at first reddish brown, closely dotted with round lenticels, then 

 dark brown, and finally white near the trunk. Practically incor- 

 ruptible. 



297 



