318 



REPRODUCTION IN PLANTS 



their life processes just where they had left off. Pre- 

 sumably they never become so entirely dry as to stop all 

 metabolism. 



Nostoc (Fig. 79) is another blue-green alga related to 

 Oscillatoria. It carries on its work and growth in much 

 the same manner but shows two interesting advances in 





7, ^V -r, O 



Fio. 78. — Oscillatoria. 1. A short .section of a filamont show- 

 in;? colls (1, 2, 3, 4) in process of divi.sion. c.b., the central body 

 corresponding to the nucleus of higher plants; ch, the chromatophore 

 or region of the cytopla.sm in which the bluish-green coloring matter 

 is locate. 2. A single cell on a larger scale .seen from the end. Lal)el8 

 as in fig. 1. .3. A filament in which one cell has died creating a weak 

 place at which the filament will break. This is the usual way in 

 which this plant multiplies the numlwr of filaments. 4. A single 

 filament drawn at ."V-minute intervals to show the amount and type 

 of movement. 1, 2, 3, 4 in fig. 4 indicate successive positions. 



