CHYTRIDIALES 



47 



(so that the places of forking are markedly swollen) and anastomose 

 frequently. The terminal or intercalary sporangia arise by swelling and 

 cutting off hyphal portions; the adjacent hyphal portions swell like 

 apophyses. At germination, a piece of the exospore is thrown off as a 

 lid by the swelling endospore and the uniflagellate zoospores are liberated 

 by a germ sac or singly. In case the sporangia germinate in the interior 

 of a host cell, the wall of the latter is pierced by an emission collar. 



In addition to sporangia, hypnospores have also been observed. A 

 certain hypha undergoes longitudinal and transverse divisions so that 



Fig. 31. — Nowakowskiella ramosa. 1. Mycelium showing numerous anastomoses and 

 swellings which will later develop zoosporangia. Below to the left, an intercalary zoosporan- 

 gium with bilateral apophyses. 2. Zoospores. 3. Proliferating zoosporangium, the lid 

 is still visible in the old one. 4, 5. Primordium of hypnospores. ( X 608 ; after Butler, 

 1907.) 



the outer cells change to thick-walled spores (Fig. 31, 4 and 5). Their 

 germination is still unknown and their morphological significance 

 still obscure. 



Both Physoderma and Urophlyclis are marked by the high develop- 

 ment of their hypnospores which in Physoderma are spherical or ellip- 

 soidal, in Urophlyctis flattened on one side. The peculiarities of their 

 structure and development have been little investigated, so that their 

 systematic classification offers great difficulties. In numerous species 

 only the hypnospores are known. 



In Physoderma macuLare {Cladochyirium Alismatis) on leaves and 

 stems of Alisma sp. (Clinton, 1902), the zoospores are uniflagellate; 



