4 FAMILIAR TREES 



Linn&us's species, Betula alba, includes several 

 fairly distinct forms. Of these, B. verruco'sa Ehrh. 

 is distinguished by its longer pendulous branches 

 having - white resinous tubercles on their bark, as 

 also occasionally on the leaves, by its conical buds, 

 by the reflexed sickle-shaped side lobes of the 

 scales of the fruiting catkins, and by the leaf. This 

 is rhornboidally triangular, its long stalk passing 

 abruptly into the blade, its veins projecting from 

 the upper surface of the blade, and its point abruptly 

 " acuminate," or tapering. B. glidino'sa Fries, on 

 the other hand, is often a mere shrub ; its buds are 

 egg-shaped, the side lobes of the scales of its fruiting 

 catkins are erect ; and its leaf is rounded, or even 

 heart-shaped, at the base, and has its veins projecting 

 from the under surface, and its point acute, but not 

 drawn out. The northern form of this last, known 

 as B. pubes'cens Ehrh., differs mainly in the absence 

 of tubercles and in the downiness of the leaves, 

 peduncles, and twigs. In all the forms the branches 

 succeed one another in Avhat is termed a " cymose " 

 manner, each axis being comparatively short ; and 

 the somewhat thick leaves on slender stalks, with 

 broad " stipules " at the base and doubly toothed 

 margins, appear before the maturity of the catkins. 

 This takes place in April and May, but even in 

 February the pollen-bearing catkins may be seen 

 forming on the twigs. 



These " male " catkins are borne at the ends 

 of the shoots of the previous year, and are not 

 protected by any winter bud-scales, whilst the 

 "female" or fruiting catkins terminate lateral dwarf 



