CHAPTER XVI. 



CEDOGONIUM. 



309. CEdogonium is ;ilso an alga. The plant is sometimes 

 associated with sjjirog\ ra, and occurs in similar situations. Our 

 attention was called to it in tlie studv of chlorophyll bodies. 

 These we recollect are, in this plant, small oval disks, and thus 

 differ from those in spirog5'ra. 



310. Form of oedogonium. — Like spirogyra, cedogonium 

 forms simple threads which are made up of cylindrical cells 

 placed end to end. But the jilant is yery different from any 

 member of the group to whith spirogyra belongs. In the first 

 place each cell is not the ecpiivalerjt of an indiyidual plant a-S in 

 spirogyra. Growth is localized or confined to certain cells of 

 the thread which divide at one end in such a way as to leave a 

 peculiar o\"crlapriing of the cell walls in tlie form of a series of 

 shallow caps or vessels (fig. 144), and this is one of the character- 

 istics of this genus. Other differences we find in the manner of 

 reproduc tion. 



311. Fruiting stage of oedogonium. — Material in the fruiting 

 stage is qiiite easily obtainable, and may be preserved for study 

 in formalin if there is anv doubt about obtaining it at the time 

 we need it for sttidy. This condition of the plant is easily de- 

 lected because of the swollen condition of some of the cells, or 

 by the pre-ence of brown bodies with a thick wall in some of the 

 cells. 



312. Sexual organs of cedogonium. Oogonium and egg.— 

 The enlarged cell is the oogonium, the wall of the cell being the 

 wall of the oogonium. (Seeiig. 145. j The protoplasm inside, before 



147 



