624 AQUATIC PHYCOMYCETES 



A. neo-moniliformis (cystogenus) 14 



A. arbuscula 8 



A. macrogynus 14 



Polyploidy was found by Emerson and Wilson in both A. arbuscula 

 and A. macrogynus (see p. 632). 



Certain features in the cytology of various species of Allomyces are 

 shown and explained in Figure 41. 



LIFE CYCLES 



Comparative investigations by Emerson (1938a, 1939, 1941) of a 

 large number of isolates of Allomyces from various parts of the world 

 and the work of McCranie (1942) and Teter (1944), have revealed some 

 extraordinary facts concerning the life history of these organisms. As 

 may be recalled, Kniep (1929) had discovered that in A. javanicus the 

 planonts 1 emerging from resting spores gave rise to sexual plants upon 

 germination. The male and female gametes produced by these plants 

 fuse to form zygotes which, upon germination, develop into asexual 

 thalli. It was clear that an alternation of generations was present (Kniep, 

 1930). 



This "long-cycled" life history (Fig. 42, p. 626), which was ob- 

 served by Kniep in Allomyces javanicus, Emerson designated "Eual- 

 lomyces." Certain of the strains with which he worked, however, failed 

 to exhibit a sexual phase. Closer scrutiny revealed that in them two 

 other different life cycles existed. Of these, the one exemplified by A. 

 moniliformis, A. cystogenus, and A. neo-moniliformis (Fig. 43, p. 629) 

 he called "Cystogenes" and the other represented by A. anomalus, 

 "Brachyallomyces." 2 



At this point it should be drawn to the reader's attention that the 

 Euallomyces, Cystogenes, and Brachyallomyces life cycles have, sub- 

 sequent to the early work on Allomyces, also been found in various 



1 Called "R.S. zoospore" by Emerson (1941; 89). Emerson and Wilson (1954) 

 refer to the resting spore (except in Brachyallomyces) as a "meiosporangium" and 

 to its swarmers as "meiospores." 



2 "Euallomyces," "Cystogenes," and "Brachyallomyces" are used as subgeneric 

 names by Emerson (see Allomyces, pp. 670-678). 



