Minnesota Plant Life. 



191 



to the exclusion of other varieties, being employed in tanning. 

 The substance known as tannin is abundant in hemlock bark 

 and by its action upon hides they are cured and converted into 

 leather. 



The tamarack. The tamarack differs from the other Min- 

 nesota pines in its habit of shedding its leaves in autumn. The 

 leaves are never of the dark rich green of the spruces, firs or 

 pines, but are of a paler color. In autumn they turn golden yel- 

 low before they fall and after the severe frosts of November 



Fig. 73. Tamarack swamp with .sedge border. After photograph by Williani.s. 



they separate from the twigs by means of cork layers and the 

 tree passes the winter in a leafless condition. Tamaracks oc- 

 cupy wet ground, forming by their growth the well-known 

 feature of the landscape known as the tamarack swamp. The 

 cones of the tamaracks are small. The wood is hard, resinous 

 and durable, weighing twice as much as that of white cedar, and 

 is used in the manufacture of railway ties, as fence poles and 

 for fire-wood. Occasionally, too, it is manufactured into tele- 

 graph poles. 



