PHACIDIALES 



309 



denser content and deeper staining properties. They grow to fertile 

 hyphae, which bore under the plectenchyma in a group and reach a 

 length of six cells (Fig. 207, A). Meanwhile the knot thickens the cell 

 walls on its outer surface, and becomes a flat, brown, sclerotic mass. The 

 fertile hyphae stow themselves on the hard basal peridial layer, bend 

 irregularly and fork. 



irffi 



Fig. 205.— Cry ptomyces Pteridis. Section of young hypertrophied fronds of the brake 

 covered with acervuli. ( X 330; after Killian, 1918.) 



The further development proceeds from the three more strongly 

 developed end cells (Fig. 207, A, cells a, b, c). Cell a later elongates so 

 that only the subterminal cell b and the terminal cell c retain their 

 characteristic cubical appearance. In late summer, the subterminal 

 cells of two neighboring fertile hyphae develop copulation papillae toward 

 each other and the nucleus migrates from one cell to the other while the 

 rest of the fertile hypha collapses and disappears. 



