Western Service Berry TreeThe Western Service-berry (A. alnifolia, Nutt.) has a thick, roundish leaf, broad and toothed, which makes it a handsome foliage tree. Its large, juicy, fine-flavoured berry commends it to horticulturists as worthy of cultivation. It grows over a vast territory which extends from the Yukon River south through the Western States, and east to Ontario, Michigan and Nebraska.
Widely distinct as is this species from A. Canadensis when individuals from distant localities are compared, these differences become less marked as each species is studied nearer and nearer the regions where their ranges overlap. It is believed that in these two we have the offspring of a single species which came from the North, and, spreading east and west on the slopes of the Rocky Mountains, became modified by climate into two distinct species as we see them to-day.
Comparisons of specimens taken at regular intervals on both sides of the mountains form a most interesting chain of evidence to support the theory of a common origin. Fossils of the Glacial Period show clearly the characteristics of the ancestral type.