PHYCOMYCETES 245 



branched conidiophores. On germination the conidia 

 either emit a germ-tube or liberate zoospores. Aerial; 

 endoparasitic on living plants, mostly on leaves. 



Peronosporeae. 



Asexual reproduction by zoospores. Aquatic fungi 

 parasitic on fishes, insects, and plants. Saprolegnieae. 



Chytridieae 



The most primitive forms of fungi at present known, 

 almost or entirely destitute of mycelium, and in many 

 respects closely approaching some of the lowest forms of 

 animal life, from which Dangeard suggests the fungi have 

 descended through such forms as Polyphagus, etc. 



Either aerial and parasitic in the tissues of plants, or 

 aquatic and parasitic on fresh - water algae, fungi, or 

 infusoria. 



Many of the so-called species are imperfectly known ; 

 one, however, described in detail by Nowakowski, is sum- 

 marised as follows by De Bary : 



' Polyphagus euglenae^ a parasite upon resting Euglena 

 viridiS) has become the best known of the Chytrideae 

 through Nowakowski's beautiful investigations. The 

 swarmspore [zoospore], when it has come to rest in the 

 water, becomes spherical in shape, and at once puts out 

 hair-like, tubular rhizoid processes in indefinite directions. 

 If one of these encounters a resting Euglena it penetrates 

 into its body, destroying and exhausting it to supply food 

 to the parasite. The parasite then begins to increase in 

 size, the rhizoid tubes become larger and thicker, and new 

 ones are formed which throw out branches, and attack and 

 destroy any new Euglenae which they encounter. In this 



