1 64 



DISEASES OF TREES 



August I have found green leaves beset with the withered 

 aecidia. 



Serious damage is done only when the young silver firs are 

 situated amongst badly infested cowberry-bushes, and when the 

 greater part of the leaves contract the disease. The aecidium 

 form possesses a facultative character that is to say, it may be 

 absent without endangering the existence of the parasite whose 



FIG. 94. a, the branch of a silver 

 fir on the under side of whose 

 leaves two rows of the recidia 

 of M. Goeppertiana (ALcidiinn 

 columnare) have developed ; &, 

 the aecidia magnified. 



FIG. 95. An aecidium of M. Goepper- 

 tiana, a, in the tissues of a leaf of 

 the silver fir ; b, the strings of 

 oecidiospores with intermediate 

 cells ; c, germinating secidiospores. 



sporidia are capable of germinating on, and of directly infecting 

 cowberry- plants. 



Where damage is to be apprehended from the columnar rust 

 of the silver fir during the regeneration of a wood, one may reduce 

 the chances of an outbreak by rooting out diseased cowberry- 

 plants. On account of their striking appearance, these are not 

 difficult to find. 



MELAMPSORA TREMUL^ * 



Under the name Melampsora populina, the Poplar-rust, are 

 denoted the fungus-forms belonging to this genus which are 

 met with on various species of poplars, and which await more 

 thorough and exact investigation. 



Forms are met with on Populus tremula whose cushion-like 

 * [Occurs in England, and requires investigation. ED.] 



