I 50 Bi'itish Fitngi, 



resting time is over and produces a zoosporangium 

 like the non-conjugating plants, (figs. 78 — 82). 



'' PolypLagus, tlierefore, is essentially characterized 

 by the gametes with their rhizoids, the mode of 

 forming the zygospores, and the production of the 

 zoosporangium or of swarm-cells from it. It may be 

 assumed to be possible for these swarm-cells to 

 develop directly into gametes ; but an indefinite 

 number of generations of non-conjugating plants are 

 in fact interposed between two successive gamete- 

 generations. The gametes in each pair behave diffe- 

 rently in conjugation^ as has been shown, and the 

 species is dioecious. Which of the two should be 

 called the male and which the female is not easy to 

 determine, and must not be further discussed in this 

 place. It is evident that we have before us an inter- 

 mediate case between the ordinary forms of oogamous 

 [= gametes of equal form and size] and isogamous 

 [= gametes of unequal size] conjugation.^' 



Chytridie^. 



Hyphse often absent or obsolete, hence the 

 sporangia are often destitute of mycelium, at least very 

 soon after their formation j asexual reproduction by 

 zoogonidia which are produced simultaneously by the 

 partition of the protoplasm contained in the zoo- 

 sporangia; after escaping from the zoosporangia, the 

 zoogonidia become encysted and form resting-spores ; 

 single vegetative cells or pairs that conjugate also in 

 some cases become transformed into resting-spores. 

 Either aerial fungi parasitic on plants, rarely sapro- 

 phytic, or aquatic and parasitic on algse^ fungi and 

 infusoria. 



