334 THE VEGETABLE WORLD. 
offer. They are trees or shrubs, with simple alternate leaves 
nearly orbicular in shape, with primary veins running nearly 
straight from the midrib to the margin; stamens usually distinct; 
ovary superior and two-celled; fruit membranous, indehiscent 
and one-celled; seed pendulous. The Birch-tree, Betula alba, is 
monecious, with alternate leaves, ovate and peteolate, accuminate 
and dentate or doubly dentate, green and glossy above, of a pale 
glabrous green below. Their straight upright stems, smooth 
silvery bark, long, round, slender, flexible, and pendulous branches, © 
render the Birch a graceful ornament in the landscape. 
The Birch is in flower in the month of April, when the white 
silvery bark produées the happiest effects contrasted with the 
deeper and more sombre tints which the trunk of the Elms and 
Oaks present. y 
The Alder, Alnus glutinosa, has stalked simple stipulate leaves. 
F lowers in male and female catkins, the male flowerets loose at : 
cylindrical, usually in threes on the pedicle of the scale; stamens, 
Bract bearing two Ripe Catkin. Bract bearing three flowers 
female flowers. of the Alder. 
Fig. 374. ie lene 
ale flowerets 
_ three or four inserted at the base of the divisions. Fem ee 
in dense ovate catkins, two together on roundish sessile fleshy ee 
with four smaller ones at their base, each with a small Ovary) ak 
two one-seeded cells. The glutinous leaves, red sap, and wi he 
fruit distinguish the only British species of Alnus from © 
Birches. : es 
of rivers, an 
are of # 
