OBSERVATIONS ON THE GENUS PyTHIUM. 497 



How is it then that at a late stage in the development of 

 such a fungus as this Pythium, the starch grains and all 

 traces of cell contents — even cell walls — disappear ? Without 

 entering into details, it appears at least highly probable that 

 the remaining changes in the cell contents are effected by 

 Bacteria, carried into the invaded tissues by the hypbse of 

 the Pythium; that these Bacteria reduce the rest of the 

 protoplasm and nucleus first to a soluble mass, and then cause 

 the dissolution of the starch grains. But facts point to the 

 possibility that the action of the Bacteria in such cases is 

 taken advantage of by the fungus, and that it is not till a very 

 late period that the mycelium of the latter suffers from the 

 dominance of the former and eventually becomes in part a prey 

 to its companion, having meanwhile formed its well protected 

 oospores and conidia, which lie unhurt among the rotting 

 debris. 



Pythium proliferum.^ 



The next example of this genus, the life-history of which I 

 have thoroughly examined, is P, proliferum, discovered by 

 De Bary on decomposing insects in Avater about 1860. In 

 many respects, especially in regard to the sexual organs, &c., 

 it resembles P. De Baryanum so closely as to be hardly dis- 

 tinguishable from it; important differences indeed, can hardly 

 be said to exist. It occurs, however, only as a saprophyte, 

 and all attempts to grow it on living plants have failed, though 

 its cultivation on dead cress-seedlings — the seedlings being 

 killed by plunging into boiling water — is very easy. Perhaps 

 the best distinctive character is to be found in the zoo spo- 

 rangia, which are formed in large numbers and retain their 

 power of forming zoospores for long periods, and are pecu- 

 liarly beaked. The mycelium resembles that of P. De Bary- 

 anum in all essential respects, ramifying in the dead tissues 

 and finally putting forth free branches, which rapidly spread 



^ ' Pringsb. Jalirb. f. wiss. Bot.,' vol. ii, p. 182 ; ' Beitrjige z. Morph. u. 

 Phjs. d. Pilze/ 1881, 11. iv ; 'Bot. Zdt.,' Seut., ]881, p. 558. 



