PROTOBASIDIOMYCETES 



429 



and in the regions where the hyphas are abundant the amount of 

 starch is distinctly less than in those not pervaded by the fungus. 

 In the stem, according to Clinton, the mycelium is found espe- 

 cially in the pith, in a more or less zonal area situated near the 

 fibrovascular system. The young mycelium is more readily seen 

 on account of the greater amount of coloring matter which it 

 contains. 



The structure of the spermogonial stage has been carefully stud- 

 ied by Richards. His work indicates that the spermogonia arise as 

 a bundle of septate threads which press against the surrounding 



a b 



Fig. 209. C^eoma Stage of Gymnoconia Peck/ana. (After Clinton) 

 a, general effect on leaf ; li, cross section through a young sorus 



cells so as to cause them to collapse, and these injured cells are 

 finally penetrated by the mycelium. On reaching full growth small 

 spore-like bodies are abscised from the ends of each thread ; and 

 when produced in quantity, the epidermis is ruptured, or punctured, 

 and the spores ooze out as a small glandular droplet. It has not 

 been shown with certainty that these spores have been germinated. 

 The observations upon a budding habit suggested by early ob- 

 servers may have concerned themselves with yeast cells asso- 

 ciated with the spores and accidentally introduced into the culture 

 drop. 



