79 
It is curious to mark in the same genus what diversity 
is sometimes exhibited in the mode of growth, peculiar 
habits, and choice of abode, of the different species. Whilst 
Alnus glutinosa (our common alder) shows such decided 
preference for river scenery, the hoary or silver-leaved 
alder quits the valley for the mountains, and grows at 
an elevation of 6000 feet above the level of the sea. A 
stunted growth is the consequence of its ambitious 
propensities; for whilst the former attains a height of 
from thirty to forty feet, the latter is a mere shrub, its 
main stem being scarcely thicker than the human arm. 
According to Linnmus, the birch and the alder are 
joined in the same genus. They differ widely in their 
general aspect, the birch being remarkable for the 
elegance of its form and the delicate tint of its foliage; 
whilst the alder sometimes “ puts on so much of the 
bold resolute character of the oak, that it might be 
mistaken for that tree, but for the intense depth of its 
green hue.” It is useful for a variety of purposes. 
Immersed in water, “ it will harden,” says Evelyn, “ like 
a very stone; ” and on that account was used by the 
ancients, and is still used by the moderns, to form a 
foundation for buildings erected in swampy situations. 
In the infancy of navigation it was employed by them in 
