EXPLANATION OF THE PLATES. 



PLATE I. REPRODUCTION IN ALG^E AND FUNGI. 



Figs. 1 and 2. Filamentous Algae in conjugation, (p. 23) after 

 Smith. In Fig. 1, (Mesocarpus,) the endochrome of both the 

 conjugating cells is evacuated into the connecting tube formed 

 by the fusion of their papillary outgrowths, and the spore is 

 matured in the same place ; in Fig. 2, only one of the conjugat- 

 ing cells evacuates its contents, which are received into the 

 other, where the spore is formed from the fusion of the two 

 endochromes. In this figure conjugation is shown between the 

 cells of distinct filaments, as well as between two adjoining cells 

 of the same filament a circumstance showing, as Mr. Smith 

 remarks (Trans. Microsc. Soc., II. 70), that the importance of 

 variations in this respect, as distinctive characters, has been 

 over-rated by some Naturalists. 



Fig. 3 (from Ralfs) shows the process of conjugation in the 

 Desmidieae (Closterium acerosum). The evacuation of the cells 

 takes place by the separation of their valves, and the spore is 

 formed, as in Mesoca/rpus, midway between the cells. 



Fig. 4 (also from Ralf s) represents a process of endogenous 

 multiplication in the germination of the spore of Closterium 

 (P- 27). 



Figs. 5 and 6 (Eunotia turgida, from Thwaites), illustrate the 

 process of conjugation in the Diatomacese, in which the effused 

 endochromes are resolved either at once, or at a very early 

 period, into two spore-masses, which are ultimately trans- 

 formed into frustules of a much larger size than their parents. 

 The genetic cycle is supposed to be completed by their breaking 

 up into frustules, like those originally concerned in the process 

 of conjugation (p. 28). 







