CHAPTER XVI. 



CEDOGONIUM. 



309. (Edogonium is also an alga. The plant is sometimes 

 associated with spirogyra, and occurs in similar situations. Our 

 attention was called to it in the study of chlorophyll bodies. 

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

 differ from those in spirogyra. 



310. Form of cedogonium. Like spirogyra, oedogonium 

 forms simple threads which are made up of cylindrical cells 

 placed end to end. But the plant is very different from any 

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

 place each cell is not the equivalent of an individual plant as 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 overlapping of the cell walls in the 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 

 reproduction. 



311. Fruiting stage of oadogonium. Material in the fruiting 

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

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

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

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

 by the presence of brown bodies with a thick wall in some of the 

 cells, 



312. Sexual organs of oedogonium. Oogonium and egg. 

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

 walloftheoogonium. (See tig. 145.) The protoplasm inside, before 



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