292 



The Black Spruce. 



Let us pass now to the consideration of the parasites of 

 the spruce. Perhaps no species of flowering plant is wholly 

 free from the attacks of animal or vegetable parasites, but 

 some are much more liable to these attacks than others. 

 One species may be subject to the attack of a single parasite, 

 another, of a half dozen or more. I have sometimes thought 

 that the greater the susceptibility of a plant to variation 

 the greater its liability to parasitic attacks. Certainly the 

 variable black spruce is obnoxious to many parasitic foes. 



Arceuthobium pusillum, a brief account of which was for- 

 merly read before the Institute, is one of these. Like many 

 other parasitic plants it is destitute of true leaves. Botani- 

 cal ly it is related to the mistletoe and by way of distinction 

 it might be called the spruce mistletoe since it is thus far 

 peculiar to that tree. It often occurs in abundance fring- 

 ing the younger interuodes of the living branches by the 

 multitude of the plants. Having once attacked a tree it 

 continues to prey upon it year after year, growing with its 

 growth and thriving with its thrift. The remarkable fact 

 about it is that thus far it has been detected on those s: ruces 

 only which grow in swamps or on and around sphagnous 

 marshes. It has not yet been seen on the typical forest 

 spruce. Though this plant was first discovered but little 

 more than three years ago it is now known to occur in five 

 counties of the state. I have not heard of its discovery 

 beyond the state boundaries. It is not positively known 

 to kill the tree it attacks but it is probable that it sometimes 

 does. Dead trees occur which bear the marks of its former 

 presence. 



Peridermiwn decolorans is another foe to the spruce. It 

 is a species of fungus allied somewhat to the rust of the 

 grain fields, but more closely to the cluster cup fungus. 

 It consists of small scattered tubercles which burst forth 

 from the leaves of the spruce, rupture at the apex and reveal 

 a mass of yellow, dust-like spores within. The affected 

 leaves become yellow and probably drop from the branch 



