THE PLANT-CELL. 



19 



cipal forms of cells, wliloU la giveu below iu a hliglitly modifled 

 form : 



Cell globular or 

 ovoid, in section 

 round or oval Spheroidal. 



Cell polyhedral. Polyhedral. 



Cel 1 a parallelo- 

 pipedon, in section 

 rectangular Cuboidal. 



Cell tabular, 

 witli an elongated 

 rectangular sec- 

 tion Tabular. 



Outline smootli, 

 or without promi- 

 nences. 



Cell short 

 (Par enchyma-< 

 tons). 



With prominences. 



Cell elongated. ■ 



Cell ramose, 

 havinjr short and 

 irregular projec- 

 tions Bamoae. 



Cell star-shap- 

 ed, having lung 

 projections which 

 are more regular. . Stellate. 



Cell cylindrical, with its ends at 

 right angles to its axis, or but little 

 inclined Cylindrical. 



Cell prismatic, with its ends at 

 right angles to its axis, or but little 

 inclined Prismatic. 



Cell fusiform [cylindrical or pris- 

 matic], with its ends oblique and 



pointed Fusiform 



[Prosenchymor. 

 tous). 



20. — When one or more sides of a cell are not in contact 

 ■with other cells, as is the case with those cells which com- 

 pose the surface of plants, the free sides are generally con- 

 vex, and they often become more or less prolonged, sometimes 

 in a curious way. The velvety appearance of the petals of 

 many plants is due to such prolongations of the free sides of 

 the surface cells (Fig. 8). Of a somewhat similar nature are 

 the tubular extensions of the surface cells of young roots — 

 the root-hairs. And here we may also place the curious star- 

 shaped cells which project into the intercellular spaces in the 

 interior of the stem of the water lily (Fig. 9), and those 

 which compose the pith of certain rushes (Fig. 95). 



21. — In the unicellular plants each cell is an independent 



