FERTILIZATION AND FRUIT-FORMATION INT CRYPTOGAMS. 



57 



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

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

 any intermediate stage; or in others, the tube, wliich represents the embryo, 

 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- 

 sporese of spores on deudritically-branched hyplite growing out through the 



Fig. 205. — Fertilization, fruit-formation, and spore-formation in tlie Peronosporete. i 



' A bunch of tn'apes attaclted by tlie Vine-Mildew. 2 Spores on branched stalks projecting throngh a stoma of a Vine-leaf 

 3 Fertilization in Peronospora viticota. * A single spore. <> A single spore the contents of wliich are dividing into swann- 

 spores. 8 A single swarmspore. ' natural size; 2x80; s-6x350; «x3S0. (3-6 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 pi'ocess. 



The SiphonaceiB exhibit a diftei-ent mode of fertilization from those processes 

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

 canal respectively. All the Siphonacese 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 Vaitcheria (see vol. i. Plate I. fig. a, 

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



