XII.] 



PINE-BLISTER. 



259 



corticola\ It is thus seen that the fungus Peri- 

 dermium Pint was regarded as a parasite of pines, 

 and that it possessed at least two varieties, one in- 

 habiting the leaves and the other the cortex : the 

 " varieties " were so considered, because certain 

 differences were found in the minute structure of the 



yx, 



FIG. 39 Vertical section through a very young SEcidium of Peridermiunt Pint 

 (var. acicola), with part of the subjacent tissue of the leaf. A, the mycelium of the 

 parasitic fungus running between the cells of the leaf: immediately beneath the 

 epidermis of the leaf, the ends of the hyphae give rise to the vertical rows of 

 spores (b), tha outermost of which (p) remain barren, and form the membrane of 

 the blister-like body. The epidermis is already ruptured at / by the pressure of 

 the young JEcidium. (After R. Hartig : highly magnified.) 



addict, and spermogonia. The disease is popularly 

 denoted " Pine-blister." 



If we cut thin vertical sections through a leaf and 

 one of the smallest blisters or <zcidia> and examine 

 the latter with the microscope, it will be found to 

 consist of a mass of spores arranged in vertical 

 rows, each row springing from a branch of the 



S 2 



