216 PRACTICAL BOTANY 



CONFERVOIDE^E 

 (EDOGONIUM 



Various species of plants belonging to this genus are to be 

 found growing in fresh water : they are green, filamentous, un- 

 branched Algae, and are attached at the base to the external 

 surface of submerged plants, stones, &c. The apex of the 

 filament is in some species extended into a thin, hair-like 

 process : there is often considerable irregularity in the thickness 

 of the filament, by which character, as well as by the peculiar 

 transversely striated markings of the cell-walls, these plants 

 may be distinguished. 



I. Mount filaments of CEdogonium in fresh water, having 

 gently scraped them off from the surface to which they were 

 attached, and examine them under a low power : observe 



1. The long unbranched filament, of uneven thickness, termi- 

 nated at the apex either by a rounded cone, or by an attenuated 

 process : note also at the base the irregularly lobed disk of 

 attachment. 



2. The septa, dividing the filament into a series of cells, with 

 green-coloured contents. 



3. At the upper ends of many of the cells transverse striae 

 are to be seen : these are indications of past cell-divisions. 



Examine the filaments under a high power, and pay special 

 attention to these striae and other irregularities of the otherwise 

 smooth cell-walls. It will then be seen that the striae are small, 

 sharp-edged, ring-like projections on the outer surface of the 

 wall : also that a single corresponding stria is to be found, more 

 or less distinctly marked, at the base of each cell. 



In some cells an annular ingrowth of the cell-wall may be 



