FERTILIZATION AND FRUIT-FORMATION IN CRYPTOGAilS. 57 



which subsequently, in some cases, puts out sac-like processes and branches and 

 fashions itself into the likeness of the mother-plant without passing throujjh 

 any intermediate stage; or in others, the tube, which represents the embrj^o, 

 produces first of all from its protoplasm a number of swarmspores. These roam 

 about for a period and then seek out a convenient spot where they come to rest 

 and develop into new individual plants. The additional production by Perono- 

 sporeae of spores on dendritically-branched hyphse growing out through the 



Fig. 205. — ^Fertilization, fniit-fomaation, and spore-formation in the Peronosporeffi. 



1 A bunell of grapes attacked by the Vioe-ilildew. a Spores on branched stalks projecting tJirongh a stoma of a Yine-leal 

 s Fertilization in Peronospora vUicola. * A siniile spore, s \ single spore the contents of which are diridlng into swarm- 

 spores, 6 A single swarmspoie. > natural size; ^xSO; »-^xS50; «xSSO. p-« after De Bary.) 



stomata of the green host-plants is shown in fig. 205°, but an opportunity will 

 occur later on of discussing the details of that process. 



The Siphonaceee exhibit a different mode of fertilization from those processes 

 which involve the preliminary construction of a fertilization-tube and a conjugation- 

 canal respectively. All the Siphonace£e live in water or on damp, periodically 

 submerged earth; they contain chlorophyll and are neither parasites nor sapro- 

 phytes. We may take as a type of this group of plants, which includes forms 

 of great diversity, a species' of the genus Vaucheria (see vol. i. Plate I. fig. a, 

 and text p. 23) and use it also to illustrate the processes about to be considered. 



