Classification. 167 



growing from one and becoming blended witli tlie 

 other^ thus placing tlie protoplasm of the two sporidia 

 in direct communication. In some instances conju- 

 gation takes place before the primary sporidia break 

 away from the promycelium. After conjugation a 

 slender germ-tube is formed which receives all the 

 protoplasm from the two united sporidia, and if 

 developed upon the proper host plant, penetrates into 

 its tissues and forms a mycelium which in turn 

 produces a new crop of resting-spores. In some 

 species the process is more complicated; the germ- 

 tubes produced by the primary sporidia after con- 

 jugation, give origin to a second set of sporidia, 

 secondary sporidia^ these in turn produce germ-tubes 

 capable of penetrating the tissues of the host, and 

 giving origin to resting-spores. The above mode of 

 development takes place when the resting-spores 

 germinate in pure water, but when germination takes 

 place in a nutrient solution Brefeld has shown that 

 the results are quite different ; instead of a short 

 promycelium producing secondary sporidia that con- 

 jugate at once, the promycelium continues to grow 

 into a dense branched mycelium which eventually 

 produces sporidia, either in the liquid or on branches 

 that rise into the air ; or the promycelium contmues 

 to develop, like the sprouting fungi, by gemmation or 

 the production of numerous, minute, elliptical cells 

 which become detached as in the genus Saccharomyces, 

 The sporidia produced in a nutrient solution do not 

 conjugate. De Bary considers the conjugation of 

 primary sporidia produced under normal conditions, 

 that is in water, as a sexual act, a view opposed by 



