THE FUNGI WHICH CAUSE PLANT DISEASE 



363 



The seciospores are borne in secia which rest in orange or 

 yellow spots often strongly thickened. Pycnia abound. The 

 aecium with its thick peridium is erumpent and projects to 

 some distance above 

 the host surface, this 

 character giving rise 

 to the separate form- 

 genus, Roestelia. The 

 peridial margin which 

 may be lacerate or 

 fimbriate is used in 

 specific characteriza- 

 tion. The spores are 

 borne and function as 

 in ordinary secia. 

 They bear several germ 

 pores. 



jEciospores germi- 

 nate at once and if 

 they fall upon suitable 

 coniferous hosts bring 

 about infection. The 

 mycelium penetrating 

 the leaf or branch 

 often induces large 

 hypertrophy. 



In spring in moist 

 weather the telio- 

 spores are found in 

 spore masses com- 



j r .1 Fig. 264.— Gymnosporangium teliospores. a, G. cla- 



posed OI tne spores, variseforme; 6, G. globosum; c, G. macropus; d, G. 

 which are usually iiidus-avis; e. G. nelsoni; /, G. clavipes. After King. 



orange or yellow, and of their long gelatinous pedicels. 



Each cell usually bears several germ pores near the septum 

 through one of which the tube emerges. 



The teliospores germinate immediately in sJiu by typical 

 4-celled promycelia and four basidiospores are produced on each 

 promycelium. 



