4 



PHYCOMYCETEAE: BLASTOCLADIALES 

 AND MONOBLEPHARIDALES 



THE organisms treated in this chapter show in very many points a 

 close relationship to the Rhizidiaceae in the Chytridiales, but exhibit 

 a greater development of the vegetative structure and a greater com- 

 plexity of sexual reproduction in most of the cases where this is known. 

 Instead of being a single uninucleate cell with a non-nucleate haustorial 

 system which immediately becomes a sporangium by enlargement and 

 internal division into zoospores, the vegetative body is a multinucleate 

 clavate, cylindrical or spherical, or hypha-like structure which may be 

 simple or branched. True septa are wanting except to delimit injured 

 regions or sporangia or gametangia, but coarsely perforated pseudosepta 

 occur in Allomyces and "cellulin" plugs may occur at the constrictions 

 in Gonapodya. From this vegetative body arise one to many sporangia or 

 gametangia. These organisms are aquatic or perhaps more often inhabit 

 the soil. Most are saprophytic on vegetable material but the genus 

 Catenaria contains species which may grow parasitically, in nematodes, 

 in fluke eggs, and in the case of one species (Couch, 1945a) in the hyphae 

 of the aquatic fungi Allomyces and Blastocladiella. Coelomomyces is para- 

 sitic in the larvae of mosquitoes. 



The zoospores and gametes, where motile, are as in the Chytridiales 

 posteriorly uniflagellate, with the whiplash type of flagellum. In a few 

 species in the genera Blastocladia and Monoblepharis biflagellate zoo- 

 spores have been observed occasionally. Cotner (1930a,b) demonstrated 

 that these are abnormal structures, being binucleate as well as biflagellate, 

 and that their occurrence is due to unfavorable conditions of develop- 

 ment, usually unfavorable temperature, so that the typical zoospore of 

 this whole group should be looked upon as being uniflagellate. The cell 

 walls do not give the cellulose reaction with chloriodide of zinc except 

 after treatment for some time with warm KOH or NaOH solutions which 

 apparently saponify fatty deposits in the cell walls. After such treatment 



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