54 FUNGI AXD FUXGICID1.S 



that lodge upon the tender bark of young shoots send 

 out germinating tubes and start other knots. 



^^As the season advances," says Dr. Halsted, "the 

 young knots and the fresh growth of older ones lose 

 their olive, velvety appearance, turn a dark color, and 



develop a hard incrusta- 

 tion on the surface. With- 

 in the substance of this 

 black and brittle layer 

 ^4 many spherical pits are 

 l^'d formed, and, as winter 

 advances, minute sacs are 

 produced upon the wall of 

 the cavity, that toward 

 spring bear each eight 

 oval bodies that are known 



FIG. 26. SPORES OF BKOWX ROT. ^^ ^^^ SpOrCS. IhCSC 



MAGNIFIED. escape from their long 



sacs and pass out througli a pore at the top of the cav- 

 ity, and are then carried by the winds to the surface of 

 a yonng cherry or plum 



twig, and thus begin 

 another knot, which, in 

 the course of time, pro- 

 duces a new crop of sum- 

 mer, and another of winter 

 spores, and thus the dis- 

 ease is preserved and 

 propagated." fig. 27. browk rot spores ger- 



Treatment.— The only mlxa^ixg. .magnified. 



successful treatment for a badly infested tree is to cut 

 and burn it, trunk, branch and all. All knots on trees 

 but little affected should be cut aud burned. Never 

 throw the removed knots on the ground, as spores are 

 developed off as well as on the tree. When young 

 knots appear on large limbs, or on limbs that one does 



