566 AQUATIC PHYCOMYCETES 



forming subapically the rudiment of the sporangium or the resting 

 spore, the endobiotic giving rise to a system of broad wide-lumened 

 branched rhizoids; sporangium operculate; zoospores posteriorly uni- 

 flagellate; resting spore thick-walled, epibiotic, borne like the spo- 

 rangium, germination not observed. 



A monotypic genus, saprophytic on vegetable debris in fresh water. 



Although early stages in the development of this remarkable chytrid 

 were not observed Minden did determine that the young plant consisted 

 of a short somewhat cylindrical or irregular thick-walled main axis that 

 gave rise basally to coarse rhizoids. Beneath the apex of this axis a 

 lateral outgrowth appeared which soon expanded to form a spherical, 

 at first oblique but later nearly upright, body— the rudiment of the 

 sporangium. As this rudiment continued to expand the true apex of the 

 axis was pushed aside and appeared as a blunt or rather angular process 

 on the mature thallus. The whole thallus was one-celled and filled with 

 dark, brownish, granular protoplasm, which was mostly collected in 

 the distal expanded part. The latter was then cut off by a cross wall from 

 the rest of the thallus and its contents cleaved into zoospores. At 

 maturity the sporangia were so large as to be visible to the naked eye. 

 Minden was in doubt as to whether or not he observed the resting spore 

 (Fig. 33 E). 



The genus is an interesting one from a phylogenetic standpoint, since 

 in its thallus development it approximates Blastocladiella, a member of 

 the Blastocladiales. It seems probable, however, that there will be found 

 in the future an inoperculate Macrochytrium-likQ chytrid which will 

 even more closely connect these two orders than does Minden's fungus. 



Macrochytrium botrydioides Minden 



Centralbl. f. Bakteriol., Parasitenk. u. Infektionskrankh., Abt. 2, 8: 824. 1902; 



Kryptogamenfl. Mark Brandenburg, 5 : 386, fig. 30a-c. 1911 (1915); Falck, 



Mykolog. Untersuch. Berichte, 2(2): 249, pi. 8, figs. 76-85. 1916 



Sporangia broadly ellipsoidal, with a broad rounded apex, subspher- 

 ical or somewhat long-cylindrical, variable in size, the smaller ones 300- 

 350 u. long by 200-250 [i in diameter, and the larger up to 800 u. long 

 by 650 ;jl in diameter, wall smooth, fairly thick, the outer layer cu- 

 ticularized, the inner colorless, cut off from the broad apex of the rhizoi- 



