174 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



nigra in view) ; and alba, with oval-oblong, or oval-cylindrical cones^ 

 pendulous, on longer branclilets than the others, (the geographical 

 range extending to the Rocky Mountains, on authority of specimen 

 from Bourgeau). 



In Dr. Kobert Bell's chart of the northern limits of trees forming 

 the Canadian forests, the two spruces, alba and nijra are lined 

 together. 



Prof Macoun, in the Catalogue of Canadian Plants of the Geo^ 

 logical Survey of Canada, gives two species, combining rubra with 

 nigra. 



Sir Joseph Hooker, in his tabulation in the Outlines of Distribution 

 of Arctic Plants (Linntean Transactions, 1864), gives only alba and 

 nigra, and Sereno Watson, in the Botany of California, also dismisses 

 our si)ruces in N.E. America as " two species." 



The following descriptions of the several species are not thrown 

 into systematic form, being mei-ely intended to call attention to 

 points of difference, and to suggest observation and enquii-y, so that 

 the necessary information may be obtaiiKid for the formation of 

 accurate and jjermanent diagnostic characters : 



1. PiCEA ALBA. — Link, in Linnsea, xv. p. 519. 



Ficea alba, the white spruce of Canada, is recognized at a distance, 

 from the allied species, by the comparative massiveness of the foliage 

 with which its horizontal or pendant boughs are clothed, and by its 

 glaucous or whitish-green tint, — the leaves when newly expanded 

 being pale and silvery, as if covered with the most delicate coating of 

 hoar frost. This appearance, however, is caused by the individual 

 leaves not being wholly green, but having longitudinal rows of 

 apparently white or colourless dots or spaces, owing to the non-develop^ 

 ment of chlorophyll in certain surface cells at regular intervals. The 

 old bark of the stem is grayish, not dai-k-colored, and the young 

 shoots of the year present a smooth, shining, ivory-white surface, 

 altogether destitute of trichomes or roughness of any kind. The 

 leaves vary in actual size with the vigour of the tree, but ai-e longer 

 in proportion than those of either of the other species ; the leaf-bases 

 from which they arise are arranged uniformly around the horizontal 



