CHYTRIDIALES 



49 



interior of the host a slender hypha which later branches considerably. 

 The mycelium remains very slender; in the host cells the hyphae swell 

 to turbinate cells (Fig. 32, 1), two to four of which may be joined. Where 

 they are present singly they are rounded up and surrounded by a thick 



Fig. 33. — Urophlyctis alfalfae. 1. Advanced stage of infec- 

 tion of host tissue. 2. Section of an epidermal cell with the 

 primary turbinate cells. 3. Older stage with secondary turbi- 

 nate cells. 4. Section of a turbinate cell; the nuclei have just 

 migrated from a sporogenous cell into a young hypnospore. 5. 

 A turbinate cell with mature and immature hypnospores. (1 

 X 280; 2 to 4 X 580; 5 X 560; after Jones and Drechsler, 1920.) 



wall. In multicellular structures one cell seems to 

 discharge its content into a neighboring cell, which 

 then becomes binucleate (Fig. 32, 5) and forms 

 hypnospores on a lateral process. Further details 

 are still unknown. At maturity the mycelium is 

 entirely disorganised and the hypnospores are left 

 free in the host cell (Tisdale, 1919). 



In Urophlyctis alfalfae on young shoots of 

 various species of Medicago, especially M. sativa 

 (Jones and Drechsler, 1920), the germ tube of the 

 zoospores penetrates an epidermal cell and swells to a multinucleate 

 turbinate cell (Fig. 33, 2). Peripheral uninucleate cells are separated 

 from the protoplasm periclinally. Each of these cells develop to a long 

 narrow hypha which later swells terminally into a turbinate cell (Fig. 



