1919] WESTON— DICTYUCHUS 295 



planetic" may be somewhat misleading, and necessitates a modifica- 

 tion of our conception of the condition of monoplanetism and 

 diplanetism in the Saprolegniaceae. 



Summary 



1. In the characteristics of its non-sexual reproduction the 

 fungus which is the subject of this paper shows itself to be a 

 member of the genus Dictyuchus. No sexual reproduction was 

 observed, however; hence it cannot be assigned to any of the 

 recognized species. 



2. During the formation of spores within the sporangium, the 

 walls of adjacent spores unite with one another and with the envel- 

 oping sporangium membrane, to form a polygonally chambered, 

 indehiscent structure. In this respect Dictyuchus differs funda- 

 mentally from all other Saprolegniaceae, save perhaps the doubtful 

 genus A planes. 



3. The zoospores which emerge from the sporangiospores come 

 to rest and encyst as is customarily described. From these encysted 

 spores in turn, however, laterally biciliate zoospores may emerge. 

 This repeated emergence of laterally biciliate zoospores has not pre- 

 viously been reported in any member of the Saprolegniaceae. 



4. It is the opinion of the writer that future study will prove 

 that this phenomenon may occur in other species of Dictyuchus, 

 and perhaps even in other members of the family. 



In conclusion the writer wishes to express his thanks to Dr. 

 Roland Thaxter, under whose kindly supervision these observa- 

 tions were made. 



Laboratory of Cryptogamic Botany 



Harvard University 



Cambridge, Mass. 



LITERATURE CITED 



1. Atkinson, G. F., Some problems in the evolution of the lower fungi. 

 Ann. Mycol. 7:441-472. figs. 20. 1909. 



2. Butler, E. J., An account of the genus Pythium and some Chytridiaceae. 

 Mem. Dept. Agric. India, Bot. Series 1:1-160. pis. i-io. 1907. 



3. CoRNU, M., Monographie des Saprolegniees. Ann. Sci. Nat. V. 15:5-198. 

 pis. 1-7. 1872. 



