FERTlLISAriON 



6i 



extremity and become clavate, to form antlieridia, and one of 

 these applies itself by the obtuse extremity to the face of 

 each oogonium. With this development the contents of tlie 

 oogonium become aggregated into a spherical form in the 

 centre to constitute a gonosphere. A slender tube is projected 

 from the applied end of the antheridium into the oogonium 

 until it reaches tlie gonosphere, when it ceases further growth. 

 After this contact the gonosphere becomes invested with a 

 membrane of cellulose. Its subsequent progress, as it becomes 

 mature, is to develop a thick brown epispore, and then come 

 to rest during the winter months. 



In the Entumojyhthoraccae, or tly moulds, the process of 



b 



Fig. 38. — Sexual orgaus of Peronospora. After De Bary. 



sexual reproduction is more shnple. They are produced by 

 slightly varying modes, as a result of the conjugation of 

 opposite threads. These hyphae, either within or without the 

 body of the host, produce lateral outgrowths at opposite points 

 of two different threads, which meet midway between the two 

 conjugating cells, and coalesce. The intermediate walls are 

 absorbed, and a connecting tube is formed, through which tlie 

 contents are mingled (Fig. 39). A gemma is produced on the 

 connecting canal, which increases rapidly, appropriating the 

 contents of the two conjugating cells to form a zygospore. 

 After this the empty hyphae disappear. This process may be 

 slightly modified in different species, but it follows the same 

 principle, and the mature zygospore passes into a period of 

 rest.^ 



This much is known of sexual rcproduclicm in Fungi: that 

 1 Vegetable Wasps and Plant Worms, by M. C. Cooke (18512), p. 11. 



