FILAMENTOUS ALGM. 



coccus {A, fig. lo) may divide 

 into two, so that it consists of 

 two hemispherical cells, each 

 capable of independent growth 

 (fig. 23, A). 



In the filamentous algae the 

 cells formed by such divisions 

 remain connected throughout 

 their whole extent, and as the 

 successive divisions are parallel 

 a cell row results (£, fig. 15). 

 When the divisions are in two 

 planes the cells forma flat sheet 

 (c, fig. 15); and when in three 

 planes, a mass. 



22. Filamentous algse. 



— There is a large number 

 of plants in which the vege- 

 tative body throughout life 

 has the form of a filament. 

 The green plants of this 

 sort live almost entirely in 

 water or in wet places, and 

 may be conveniently desig- 

 nated as filamentous algcB. 



23. Fond scums. — 

 Among these none are 

 more beautiful or interest- 

 ing than the pond scums, 

 represented in our waters 

 by several genera (SpirO' 

 gyra, Zygnema, Mougeotia 

 and some others *). They 



* To the same group also 

 belong the single-celled desmids 

 already described. 



Fig. 16. Fig. 18. 



Fig. 16. — A cell from filament of Spirogyra, 

 chy chloroplast (there are three in this cell) ; 

 p, pyrenoids ; k^ nucleus. Magnified 200 diam, 

 — After Strasburger. 



Fig. 17. — Two cells from filament of Zygnemaj 

 showing the gelatinous sheath greatly swollen, 

 and stellate chloroplasts, in which is a pyrenoid, 

 with the nucleus in a strand of protoplasm 

 between them. Magnified 245 diam. — After 

 Klebs. 



Fig. 18. — A cell from filament of Mougeotia, 

 The darker body nearly filling cell is the chloro- 

 plast (face view) in which are pyrenoids, ^, and 

 tannin vesicles, g. If seen from a direction at 

 right angles it would appear as a narrow stripe 

 in the center of the cell. 2, the nucleus. Mag- 

 nified about 200 diam. — After Zimmermann. 



