Betulacee—Betula. 415 
foliage of the wild forms is extremely variable in size and out- 
line, and there are some very distinct varieties in cultivation, 
such as B. a. laciniata, with deeply cut leaves, and B. a. 
populifolia, the American variety, with large triangular acu- 
minate leaves. This species has a very wide range through 
Ewrope, Northern Asia, and North America. The only objec- 
tion to the Birch is its short life. 
B. nana isa mountain species occurring in Scotland, and 
having about the same general distribution as the last. There 
are also several North American hardy species, but they are too 
near in aspect to our indigenous species to be desirable except 
in a general collection. Some of them, however, are of 
larger stature and more valuable as timber trees. 
2. ALNUS. 
Trees and shrubs in which the fleshy scales of the persistent 
cone-like female catkins become indurated and ligneous as they 
approach maturity. Stamens 3 to 5. This genus has about 
the same range in the northern hemisphere as the last, and 
extends to South America. The ancient Latin name of the 
genus. 
1. A. glutindsa. Alder.--This is the only native species. 
It is usually a shrub or small tree, though it occasionally attains 
a height of 50 to 70 feet, and it abounds in the vicinity of 
rivers and brooks. The ordinary variety may be distinguished 
by the black bark, glutinous branches, and young leaves, which 
are of an orbicular or obovate form with a wavy serrulate 
margin. The female catkins are borne in racemes, and persist 
during the winter. The variety area has golden foliage, and 
imperialis, laciniata, asplenifolia and quercifolia, have more 
or less lobed or cut foliage; the first having elegant drooping 
‘branches and fern-like leaves. This species occurs throughout 
Europe, North Africa, and North Asia. : 
2. A. cordifolia.—A very distinct South European species, 
having more the aspect of a Poplar, the leaves being nearly 
or quite glabrous, and somewhat shining, ovate or oblong- 
cordate in outline, with a serrate margin. It is a fast-growing 
tree with light-coloured bark. , 
A. incana and A. serrulata are North American species, of 
no especial interest to horticulturists. 
