126 FOREST PROTECTION 



Par. 8. Protection Against Parasites Other Than Fungi. 



A. A number of phanerogams live parasitically upon various trees, 



notably in the tropics. 



In the United States, the common mistletoe (Phoraden- 

 dron flavescens) and the dwarf mistletoe (Arceuthobium cryp- 

 topoda and pusillum) are worthy of note. (Bull. Bureau of 

 Plant Industry No. 149, pp. 14 to 17). Arceuthobium occi- 

 dentale deforms the bole and the branches of western hem- 

 lock, causing cancerous tumors (Plate VI, Forestry Bulletin 

 No. 33, p. 16). 



The damage done by these parasites is so insignificant 

 that remedies are nowhere indicated. 



B. Tree mosses, tree algae and tree lichens are variously reported as 



malefactors when occurring in such quantities that young 

 leaves and fresh shoots are smothered by them. It is possible 

 also that they interfere with the function of the "lenticels." 

 Tittandsia usneoides and Usnea barbata may be mentioned 

 as representatives of this group. The former called "Spanish 

 moss" is a flowering plant, common on trees in the Southern 

 States; the latter, a lichen, is abundant in northern swamps 

 and woods. Compare Bulletin No. 149, Bureau of Plant In- 

 dustry, page 17. 



