FOOTNOTES:
[C] Although formerly classed under PINACEAE, recent investigations show it to be the type of a distinct family.
[D] It is not intended that this key shall serve as a means of identification of any species of Salix found in Michigan, but it has added simply to give a ready comparison of the four species which are described.
[E] It is difficult to distinguish between these species in the absence of summer characters. If leaves can be found on or beneath a tree which is sufficiently segregated from similar trees as to avoid any chance for error, the summer key on the opposite page may be used.
[F] A discussion has recently arisen as to whether Betula lenta actually exists in the state, some botanists preferring the name B. alleghanensis Britt. for the tree we have so long called Black Birch. Pending further investigation the authors have thought best to retain the old name.
Ref.—Britton: North American Trees, pp. 257-8.
[G] [1] means that the acorns mature in the autumn of the first season, hence mature acorns will not be found on the tree, but on the ground beneath the tree.
[2] means that the acorns mature in the autumn of the second season, hence immature acorns will be found on the last season’s twigs, and mature acorns on the ground beneath the tree.