494 PRACTICAL BOTANY 



should be partially or completely emptied of protoplasm 

 for a short distance below the conidium. 



These conidia are capable of withstanding drought, or 

 a temperature below freezing, without losing their 

 vitality. 



VI. From a culture containing numerous conidia 

 separate a small portion, and expose it in a watch-glass 

 to a relatively considerable bulk of fresh water : examine 

 the culture at intervals under a low power. Some of 

 the conidia will be seen to germinate by the formation 

 of tubular hyphse similar to those which produced 

 them. 



De Bary and Hesse have also described how certain of these 

 swellings, differing in no structural characters from the directly 

 germinating conidia, develop as zoosporangla, by the formation 

 of a lateral beak-like outgrowth, into which the protoplasmic 

 contents pass : a division of the protoplasm then takes place, to 

 form numerous zoospores, which escape, and after a motile 

 period, settle and germinate as new individuals. This may often 

 be observed in mixed cultures on placing the specimen in a 

 considerable bulk of fresh water. 



VII. Continue at intervals the observation of those 

 cultures which have already produced conidia: the 

 formation of the sexual organs will frequently be seen 

 to succeed that of the conidia. 



a. The oogonium resembles at first the conidium in 

 being spherical, and about of equal size with it, and is 

 partitioned off by a septum ; a central spherical mass of 

 protoplasm (the ovum) is to be recognized. 



b. The antheridium arises as a branch, either from 

 the same filament as the oogonium, or from another : 

 its apex is cut off by a septum, and it comes in 



