THE PLANT-CELL. 



19 



Outline siuootli, 

 or without promi- 

 nences. 



cipal forms of cells, which is given below in a slightly modified 

 form: 



Cell globular or 

 ovoid, in section 

 round or oval .... Spheroidal. 



Cell polyhedral. Polyhedral 



Cell a parallelo- 

 pipedon, in section 

 rectangular Cuboidal. 



Cell tabular, ■ 

 with an elongated 

 rectangular sec- 

 tion Tabular. 



Cell ramose, 

 having short and 

 irregular projec- 

 tions Ramose. 



Cell star-shap- 

 ed, having long 

 projections which 

 are more regular. . Stellate. 



Cell short 

 (Pa/renehyma-- 

 tous). 



With prominences. 



Cell elongated. - 



Cell cylindrical, wiih its ends at 

 right angles to its axis, or but little 

 inclined Gylindrieal. 



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 



{Prosenehym,a- 

 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. 9b). 



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



