142 MICROSCOPIC FUNGI. 



conditions^ will germinate, and, in fact, comport 

 themselves in the manner of true spores. 



During tlie year 1861, Dr. de Bary published an 

 account* -of the discovery by him of zoospores, 

 similar to those already described in connection 

 with the conidia of the "white rusts," produced 

 from the acrospores of the mould which originates 

 the potato disease. In the same author^s memoir 

 'of 1864, already quoted, the observations there 

 made are confirmed. When the acrospores of the 

 potato mould and the parsnip mould are sown in 

 water upon a glass slide, their contents become 

 <livided, and vacuoles are formed, as already de- 

 scribed mCystopus; these parts are expelled through 

 an apical orifice, and, when free, take the form 

 of perfect zoospores, and commence swimming 

 about in the fluid surrounding them. 



These zoospores are oval, or semi-oval, with a 

 structure resembling that of the "white rusts," 

 save that the two ciliee, or vibratile hairs, proceed 

 fi'om the same point. The number of zoospores 

 from each acrospore of the potato mould is stated 

 to be from six to sixteen, and in the parsnip mould 

 from six to fourteen. Theu^ ultimate development 

 is the same as has already been described. In 

 the potato mould, the production of the zoospores 

 is much favoured by the exclusion of light. 



* Die gegenwartig herrschende Kartoffelkrankheit, ihre 

 X"''rsache und ihre Verhiitung. Von Dr. A. de Bary. Leipsig : 

 1861. 



