92 



PLECTOMYCETES 



[CII. 



mally thick. In such cases the destruction of the infected parts is necessary 

 in order to combat the disease. 



The fertile myceHum is richly branched and consists of relatively short 

 cells; it is developed mainly on the leaves or carpels of the host, and in 



Fig. 48. Exoasciis deformans (Berk.) Fuck., x looo- 



these regions asci are produced. Sometimes the mycelium permeates the 

 whole tissue and the asci arise from hyphae below the epidermal cells and 

 push up among them {Taphrina aurea), sometimes the fertile hyphae lie 

 between the epidermal cells {Magnusiella Potentillae), but in the majority 

 of cases the asci are developed above the epidermal cells and just below the 

 cuticle (Exoascus deformans). In the species of Taphrinopsis occurring on 

 Pteris the asci are produced within the epidermal cells. 



The asci either arise directly from the mycelium (figs. 49, 50) or each is 

 borne on a small, cubical stalk cell (fig. 48) which is cut off from the ascus 



Fig. 49. Taphrina aurea (Pers.) Fr.; young asci, x 500. 



