THE ALGAE 



H7 



Polar 



nodule 



Raphe 



Central 

 nodule 



Costae 



Parietal 

 plastid 



^^z^ 



Nucleus 



Fig. 134. 



Fig. 134. — Pinmdaria viridis. 

 Fig. 135. — Pinnularia viridis. 

 Fig. 136. — Pinnularia viridis 



Fig. 136. 



Fig. 135. 



Valve view of frustule. 



Girdle view showing broad parietal plastid. 



Valve view in optical section showing the centrally 



placed nucleus and the edges of the two lateral plastids 



GIKDLE 



GIRDLE 



VALVE 



Fig. 137. — Pinnularia viridis. Transverse section of the frustule 

 showing structure of the valves and girdle plates. (After 

 Midler.) 



