18 AQUATIC PHYCOMYCETES 



mon soil Phycomycetes were recoverable from the dry soil samples 

 eight years after collection. 



Similarly, Reinboldt (1951) made a series of studies, again on German 

 soils, and found species of Rhizophlyctis and Nowakowskiella, "Phlyc- 

 tochytrium n. sp." four species of Rhizophydium, and one of Chytridium 

 to be most numerous. Analysis of her samples, from 0.5 meter quadrats, 

 indicated that these soil Phycomycetes were not uniformly distributed 

 but, rather, tended to form pockets or nests. Moreover, in summer, 

 soil moisture rather than soil temperature proved the more potent 

 factor in determining the numbers of individuals (as of Rhizophlyctis, 

 for example) present. From her extensive work on the effect of excre- 

 tory products of angiosperm roots in the rhizosphere, Reinboldt con- 

 cluded that Phycomycetes, like other microorganisms, are influenced 

 by these substances. A paper of Gaertner's (1954b) includes data on 

 frequency of occurrence, numbers in relation to different habitats, and 

 other biological aspects. 



In special water and soil types, as from brackish localities (Hohnk, 

 1939, etseq.) 1 and remote coral atolls (Sparrow, 1948), phycomycetous 

 fungi have also been obtained. Hohnk (1939, 1952b, c) isolated from 

 brackish sites species of Pythiogeton, Phytophthora ("Pythiomorpha"), 

 saprolegnians, and species of Pythium. Harder and Uebelmesser (1955) 

 and Uebelmesser (1956) have recorded true chytrids from seashore 

 and strongly alkaline (desert) soils. 



Hydrobiological Aspects 



Recent studies have underlined the limnological importance of the 

 fresh-water aquatic Phycomycetes. Their position in this respect, as 

 compared with that of the bacteria, was well stated by Weston (1941) 

 when he wrote: "It is in their parasitism that these fungi attain a signif- 

 icance in limnology far surpassing that of the water bacteria; for but 

 few of the latter are destructively parasitic on aquatic animals and prac- 

 tically none on plants. In contrast there is abundant evidence for the 

 sweeping statement that not one of the groups of organisms important 

 in inland waters escapes some measure of loss from the attacks of aquat- 

 ic fungi." Similarly, in commenting on the limnological role of these 

 fungi, Welch (1952) concluded "that aquatic fungi exercise an impor- 

 tant influence on biological productivity." 



1 See Scholz {Arch. /. Mikrobiol, 30 : 119. 1958). 



