Cell Shape 



17 



growth. By this means they may become flattened or tabular 

 (fig. 21), or polyhedral (fig. 22). 



Other forms of cells are shown in figs. 23, 24, and 25. 



Fig. 20.— Stellate cell from the hori- 

 zontal septum of the air-passages of 

 the Flowering Rush {Butotnus ttm- 

 hellaius). 



Fig. 10. — Circulation of protoplasm in 

 an elongated cell of the Celandine : 

 A, the nucleus with a nucleolus. The 

 arrows indicate the direction of the 

 currents. 



Fig. 21.— Tabular cell from the epi- 

 dermis of Callitriche. 



Fig. 22. — Polyhedral ceU from the pith of Acacia Iqphantka \ 

 a^ seen in transverse ; b, in longitudinal section. 



At first the cell wall appears as a thin layer of cellulose per- 

 fectly permeable to liquids. In some cells but, little thickening 

 takes place during growth ; in many others, however, very soon 

 layers of secondary deposit are formed lining their interior 



c 



