OOSPORE-PRODUCING ALGAL FUNGI 



113 



tissues of the host. The different kinds of nuclear fusion, which 

 accompany fertiUzation, have been described previously. The oospore, 

 which is formed, acts as a zoosporangium in some cases for it gives 

 rise to numerous spores; or in other cases it produces a germ tube. 

 In most of the forms, the oogonium contains a mass of protoplasm 

 known as the oosphere. This is divisible into an outer clearer por- 



FiG. 36. — Plasmopora vilicola. A, Conidiophore with conidiospores (nearby 

 oospores); B, Haustoria; C, Swarmspore formation. A, 950/1; B. C, 600/1. {After 

 Millardcl in Die naliirlichen Pflanzenfamilien I. i, p. 115), 



tion, the periplasm, and a denser more granular central portion, the 

 gonoplasm. After fertilization, the oospore develops a thick wall of 

 two layers, an extine and intine, and becomes a resting spore. It 

 accumulates fatty substances, which are utilized when the spore 

 germinates in the spring after a long winter's rest. The family has 

 had many revisions and in order to simplify matters Pythium and 

 Albugo (Fig. 37), which are placed in separate families by some 

 8 



