ON SAPROLEGNI^. 287 



environment improve. I have drawn one or two specimens of 

 such dormant branches of the thalhis of Sapr. monoica at 

 fig. 21. I have not yet obtained oogonia of Saprolegnia 

 monoica, and must refer to the literature;^ drawings of the 

 ripe oospores are given at fig. 22, but no attempt to produce 

 them by cultivation on my part have yet succeeded. 



The immediate object of this paper, to describe accurately 

 a few careful observations in the hope that they may help to 

 stimulate others to pursue the subject, is now ended; but it 

 may be well, before concluding, to call attention to some general 

 conclusions which have been drawn lately, and on which such 

 observations as the above throw light. 



Apart from the question as to whether the Saprolegnia be 

 regarded as true Fungi or not, they may certainly be con- 

 sidered as forming a distinct group of parasitic and saprophy- 

 tic organisms inhabiting water, and multiplying by means of 

 zoospores and oospores as above described. 



As respects the asexual mode of reproduction, by means of 

 zoospores, all observers are now fairly in accord as to the main 

 facts. With respect to the processes of incomplete segmenta- 

 tion preceding the formation and escape of the zoospores from 

 the sporangium, it appears to be best explained as a pheno- 

 menon of nuclear division, in which the cell plate first 

 formed becomes used up again. Biisgen,^ who observed a 

 similar process in several other cases, draws attention to Stras- 

 burger's discovery,^ that in the development of pollen grains 

 and spores it sometimes happens that a " primary cell plate " 

 is first formed, and then disappears, as if its materials were used 

 up again. This certainly appears to explain the phenomena 

 of the division, &c., inside the sporangium of Saprolegnia; 

 but why should the protoplasm make so many tentative efforts, 

 so to speak, before once more growing out as a thallus ? Why 



1 The development of oogouia, &c., in this form is very fully given by De 

 Bary, ' Beitr. z. Morph./ &c., iv. 



" " Die Eutwicklung der Pbycomjceten-sporangieu," Jahrb. f. wiss. Bot., B. 

 xiii, 1882. 



^ ' Zell-bildung und Zell-thcilung,' ed. iii. 



