98 



The Naturalist. 



inner coat protrudes itself and elongates into a short tube, which termi- 

 nates, without the intervention of a mycelium, in an ordinary sporangium, 

 in which spores are produced asexually. 



In connection with the formation of the zygospores of PJiycomyces 

 niteas, Van Tieghem and Le Monnier have described a somewhat curious 

 but highly significant phenomenon. During the time that conjugation is 

 being effected by the arched cells, these produce on the zone adjoining 

 the transverse partitions which cut off the uniting portions, a series of 

 repeatedly dichotomous processes as represented in Fig, 2. These do not 

 appear simultaneously but in successive order, and upon one of the arcuate 

 cells before the other ^ and the authors ingeniously suggest that in this we 

 have a " first step in the differentiation of the two elements whose union 

 forms the germ- cell, an indication as yet feebly marked, but still very 

 distinct, of sexuality, in the process of conjugation." When we come 

 to the Bisconiycetes and the Lichens we shall see how the formation of 

 apparently homologous processes gives rise to the fruit-cup, so charac- 

 teistic of these groups, as well as to the so-called " paraphyses " with 

 which the cups are accompanied. 



Oospores, In the fungoid Zygosporece'^d'^ conjugating cells — whether 

 naked and motile, or stationary and clothed with a cellulose coat — are in 

 the main so similar to one another, that in the majority of cases it is 

 impossible to distinguish them as male and female. In the Oosporece the 

 case is otherwise. Here there are such well-marked morphological and 

 physiological differences between the two elements as to render distinc- 

 tion both obvious and easy, and even to necessitate the employment of 

 different terms. Accordingly the male organ is spoken of as the 

 Antlieridium, the female organ as the Oogonium, while the spore formed as 

 the result of the sexual act is conveniently designated as an Oospore. 



In this class sexual reproduction has been made out more or less 

 satisfactorily in the genera Saprolegnia and Peronospora, which may be 

 taken as types of the orders Saproleynics and Peronosporece. 



Saprolegnieoe. The Saprolegnias are fungi, not very dissimilar in some 

 of their characters from the Mucors. They make their appearance on 

 animal substances partially or wholly immersed in water, especially on 

 dead insects. Sometimes they attach living fish, not only when domes- 

 ticated in aquaria, but also in the wild state, as was pointed out by 

 Mr. Brook in the Naturalist for May, 1878. They are unicellular 

 plants consisting of long unarticulated tubular threads, whose proximal 

 ends penetrate the nourishing substratum, while the distal ones spread 

 out into the surrounding water. Under favourable conditions they 

 multiply themselves very rapidly by asexual zoospores or zoogonidia, 



