PERIDERMIUM 



323 



Simla. The American forms referred to this species are 

 quite distinct. 



Pseudoperidia solitary or scattered, large, for a long time 



Fig. 97. Peridermium Harknessi. 1, youngstem of Pinus 

 ponderosus, three years old, showing the Peridermium, two- 

 thirds nat. size ; 2, appearance of a stem, eight years old, 

 attacked by the fungus, the swollen portion being studded 

 with aecidia, two-thirds nat. size ; 3, section through 

 Fig. 2, showing the thickening of the annual rings of wood 

 caused by the presence of the fungus. 



closed and triquetrous, at length opening at the apex, orange- 

 rosy ; spores subglobose or broadly elliptical, orange, 

 verruculose, 15-18 X 10-12 /x. 



Peridermium conorum, Thiim. ( = Aecidium conorum-piceae, 



