134 THE MICROSCOPE. Sept. 



the Canadian border to Minnesota. It is easily distin- 

 guished from the coniferous trees with which it is asso- 

 ciated, by its small cones, one-half or two-thirds of an 

 inch long, pendulous at the ends of the branches ; by the 

 slender, spreading branchlets which have crowded ap- 

 parently two-ranked leaves along their sides ; and by 

 the distinctly petiolate, flattened, linear, denticulate 

 leaves, which are green above and glaucous beneath, and 

 provided with a single resin duct on their dorsal surface. 

 Its trunk is extensively employed for lumber and its 

 bark for tanning purposes. Its pitch, also, which is ex- 

 tracted from the old bark by boiling, is employed in 

 medicine for the same purpose as Burgundy pitch. 

 Tsuga Mertcnsiana occurs on the Pacific Coast from the 

 vicinity of San Francisco northward to Alaska. While 

 very similar in appearance to our Eastern species, it is, 

 when fully developed, a tree of much larger size, some- 

 times attaining a height of 200 feet. It is also straighter- 

 grained, and has a redder and usually thicker bark ; but 

 the most distinctive difference, perhaps, is in the fruits 

 and seeds, the scales of the cones being more elongated 

 and the wings of the seeds being relatively longer and 

 straighter. The wood and bark, like those of our Eas- 

 tern species, are used for lumber and tanning purposes, 

 respectively, but whether or not any commercial use is 

 made of the pitch certainly obtainable from the bark, the 

 writer is not informed. 



The barks of these two species are the only ones the 

 writer has examined microscopically. The barks show, 

 as might have been expected, a great similarity in struc- 

 ture, though there appear to be some characters which 

 we may rely on for distinguishing them. In both, cork 

 formation begins early, and in all cases where the bark 

 has been taken from stems more than a few inched in 

 diameter, the secondary cork-formations have invaded 

 the inner laytr of the bark, and bands of cork will be ob- 



