40 



COMPARATIVE MORPHOLOGY OF FUNGI 



Related to it, or perhaps identical with it, is the somewhat larger H. 

 Hedenii which is found on Zygnemaceae in North America, Europe, 

 Patagonia and Thibet. This disconnected area suggests great age. 



The Chytridieae agree in structure and development with the Rhizo- 

 phidieae, but their resting spores develop intramatrically, as in Dan- 

 geardia mamillata (Schroder, 1898) on Pandorina morum and Chytridium 

 olla on oogonia of Oedogonium. Their sporangia open by a flat lid 

 covered with blunt spines. The method of formation of hypnospores is 

 unknown; their germination takes place through the formation of a 

 simple tube which ruptures the wall of the host and forms a sessile, 

 covered sporangium. 



Fig. 24. — Entophlyctis Cienkowskianum. 1. Cell of Cladophora with a sporangiferous 

 plant. 2. Empty zoosporangium. Saccomyces Dangeardi. 3. Four-lobed haustorium. 

 4. Cell of Euglena with germinating zoosporangia. 5. Hypnospore. (1,2 X 200; 3 to 5 X 

 280; after Zopf, 1885, and Serbinov, 1907.) 



Of all these tribes, the Rhizidieae are the highest in development 

 both in thallus and in sexuality; in the monophagic forms, the zoospores 

 have partially lost their importance as central sacs and are replaced by 

 germ sacs which simultaneously serve as sporangia. 



The monophagic forms are closely connected to the Rhizophidieae 

 and Entophlycteae. In Entophlyctis Cienkowskianum, parasitic or hemi- 

 saprophytic on filaments of Cladophora, the zoospores, as in Diplo- 

 phlyciis, put forth a germ tube which swells to a germ sac and takes up 

 all the protoplasm of the zoospores. In exceptional cases, the zoospore 

 sheath may be retained as a knob as is the rule in other species, e.g., R. 

 bulligerum. The germ sac develops to a spherical or pyriform sporangium 

 discharging its zoopores through an emission collar which often projects 

 far out into the water (Fig. 24, 2). In some species aplanospores are 

 occasionally formed (Zopf, 1885). At the beginning of the cold season, 



