BEPKODUCTION 



419 



only the Algae but the Fungi afford examples of the de- 

 velopment of such cells, conspicuous among them being 

 Saprolegnia and its allies (fig. 167). These free -swimming 

 protoplasts are known as zoogpores or tfbogonidia. Each 

 on coming to rest clothes itself Vith a cell-wall, and can 

 develop into a plant exactly like the one from which it 

 arose. These zoogonidia are developed by the protoplasm 

 of a single cell dividing up into a variable but often large 

 number of separate protoplasts, the process being known as 



FlG. 168. COZNOCYTE OF MuCOT, BEABING A 

 GONIDANGIUM, k. THIS IS MOBE HIGHLY 

 MAGNIFIED IN THE FIGURE TO THE BIGHT. 



m, columella ; Z, gonidia. 



FIG. 169. ASCI, a, MIXED 



WITH BARREN HAIRS OR 

 PARAPHYSESe,/; FROM HY- 

 MENIAL LAYER OF 



x 250. 



free cell formation. Each protoplast possesses a nucleus 

 derived from the original nucleus of the cell in which the 

 formation takes place, in the manner already alluded to. 



In most cases where these reproductive cells are met 

 with they have not so simple a structure as those so far 

 described, but each is furnished with a cell-wall. They 

 are commonly called spores or gonidia, and arise in differ- 

 ent ways upon the plant, often, or indeed generally, being 

 developed in or on special organs, known as sporangia or 

 gonidangia. 



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