EEPEODUCTION 



419 



only the Algae but the Fungi afford examples of the 

 development of such cells, conspicuous among them being 

 Saprolegnia and its allies (fig. 165). These free-swimming 

 protoplasts are known as zoospores or zoogonidia. Each 

 on coming to rest clothes itself with 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 



FIG. 166. CCENOCYTE OF Mucor, BEABING A 



GONIDANGIUM, k. THIS IS MOBE HIGHLY 

 MAGNIFIED IN THE FIGUBE TO THE BIGHT. 



m, columella ; I, gonidia. 



FIG. 167. ASCI, a, MIXED 



WITH BAEBEN HAIBS OB 

 PABAPHYSES 6,f', FBOM HY- 

 MENIAL LAYEB 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. 



