288 The Black Spruce. 



survives the shock, while seamy spruces live and thrive. 

 Probably not more than one tree in fifty, on an average, is 

 seamy. Why, then, should one tree be checked by exces- 

 sive cold while forty-nine others in the same locality and 

 exposed to the same temperature remain unharmed. It 

 is barely possible that an unusually thrifty growth or an 

 excessive surcharging of the tender tissues of the sapwood 

 with moisture might give rise to conditions in which in- 

 tense cold would produce a rupture but it is hardly proba- 

 ble. It would appear to be an easy matter to determine 

 the cause of the seam by an investigation in its earliest 

 stage or soon after its commencement, but I have never 

 yet seen one in such a condition, and do not deem it worth 

 while to waste time in speculating upon the cause of this 

 curious feature. 



Another character worthy of notice is the tendency of 

 the leaves of the black spruce and its congeners to fall from 

 the branch as soon as dry. It has always been a source of 

 annoyance to the botanist that he cannot . preserve a good 

 specimen of a spruce branch in his herbarium. The leaves 

 drop from the dried branches upon the slightest agitation. 

 No matter whether the branch has been dried in a plant 

 press or out of it, rapidly or slowly, the final result is a 

 branch without leaves. I have tried in various ways to 

 overcome this difficulty, but without full success. The 

 nearest approach to successis made with specimens collected 

 early in the season while the leaves of the new shoots are 

 yet pale and tender. These young leaves adhere to the 

 branches but the old ones drop off. This feature is not 

 wholly peculiar to the spruce as it exists almost as markedly 

 in the hemlock. 



A complete knowledge of the black spruce requires an ac- 

 quaintance with its varieties. Some plants are much more 

 fixed and uniform in their characters than others. The 

 spruce is much more disposed to be variable than the hem- 

 lock. Some varieties depend upon external conditions, cir- 



