CHYTRIDIALES 



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Hyphochytriaceae. — In this family, only one form has been described 

 in detail, Macrochytrium botrydioides (Minden, 1916), saprophytic on 

 rotting fruits in water. The plants possess a short, almost cylindrical 

 main axis which spreads out at the base in rhizoids, and ends apically 

 with a blunt process. Below the tip, a branch from the main axis swells 

 clavately and later pushes aside the tip. This is abjointed from the rest 

 of the plant, and develops a sporangium (Fig. 28, 1). At its germination, 

 a lid is sharply cut off at the top and the spore mass swells, still surrounded 

 by a membrane (Fig. 28, 2). When the bulging mass has attained about 

 half the size of the sporangium, the membrane ruptures, liberating the 

 uniflagellate zoospores (Fig. 28, 3). Their motion may be amoeboid 

 with the flagellum trailing behind (Fig. 28, 4). Minden considers this a 



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Fio. 28. — Macrochytrium botrydioides. 1. Plant with sporangium. 2, 3. Swarming of 

 zoospores. 4. Amoeboid zoospores. (After Minden, 1916.) 



biological adaptation to their special mode of life, in that often they can 

 reach a substrate covered with other organisms (e.g., bacteria). 



Cladochytriaceae. — This family includes a number of saprophytic 

 or parasitic forms which possess an evanescent, very slender, filamentous 

 mycelium with peculiar swellings called turbinate cells (Sammelzellen). 

 As a result of this higher stage of development of their thallus they stand 

 far above the other Chytridiales. Since sexual processes, however, have 

 not been demonstrated with certainty, it is still impossible to determine 

 their exact position. 



Amoebochytrium rhizidioides (Zopf, 1885), growing in the slime of 

 Chaetophora, is transitional between the Rhizideae and this family. The 

 zoospores are aflagellate but capable of amoeboid movement. After 

 they have come to rest, they surround themselves with a membrane and 

 mature to large ramose mycelia. After 36 hours, the hyphae produce 

 peculiar intercalary swellings, rich in protoplasm, which are abjointed 



