FUNGI. 



243 



individuals. These latter are in some instances monoecious, and the fertilisation is then 

 brought about by antheridial branches, which perforate the oogonium, and allow the 

 escape of the spermatozoids within it, or penetrate through holes already formed for 

 this purpose in the wall of the oogonium. In other species the sexual generation is 



Fig. leS.—Cystofius cnndidus. A branch of the mycelium growinff at the apex t witli haustoria h between the cells of the 

 pith of Lepiciium sntivutn ; K conidia-bearint; branch of the mycelium ; C, D, R formation of swarm-spores from the conidia ; 

 F swarm-spores germinating ; G a swarm-spore germinating on a stoma ; // swarm-spore of Peroiiospora infestixns penetrat- 

 ing through the epidermis of a potato-stem (after Dc Bary, x 40o)- 



dioecious, and in this case the male plant forms motile spermatozoids. Figs. 8 and 9 

 (pp. 12, 13) will sufficiently illustrate the essential points in the formation of zoospores 

 and oospores. The oospores germinate directly after a period of rest'. 



* [For the most recent study of fhe Saprolegniece the monograph of Max Cornu (Ann. des Sci. 

 Nat. 1872, vol. XV) should be consulted. He divides them into groups : (i) Saprolegniecz proper, having 

 reniform zoospores with two unequal cilia attached, one before, the other behind, or oval zoospores 

 with two equal cilia attached in front. The genera fall into two series according as their filaments 

 are cylindrical or interrupted by constrictions {e. g. Rhipidium) ; in every case the wall of the fila- 

 ments consists of cellulose, and is coloured blue by Schultz's solution, (ii) MonoblepharidcB, consisdng 

 of three species of the genus Monoblepharis, and having ovate zoospores furnished with a single posterior 

 cilium ; the wall of the filaments is not coloured blue by Schultz's solution. The sexual reproduction 

 of the SaprolegniecE proper presents two cases, according as the species is or is not provided with lateral 

 branches. In the first case prolongations of the antheridia traverse the wall of the oogonium, which 

 may or may not have been previously perforated. Max Cornu has never seen spermatozoids pro- 

 duced by the antheridium, which empties itself by an influx of its protoplasmic contents; the process 



R 2 



