14 



PKOGAGATIOIT OF PLANTS. 



trace the relations of such low organisms through a 

 multiplicity of channels up to the higher forms of plants. 



Size and Fobm of Cells. — The size and form of cells 

 are infinitely varied, and, as only a comparatively small 

 number of the known species of plants have been sub- 

 jected to a careful microscopic examination, we can only 

 gather an idea of the many forms from what we know of 

 the few. Wood cells of different forms and sizes are 

 shown in figure 3. The size of cells may be said to vary 

 from Yjo of an inch up to '/,„„„ of an inch in diameter, and 



there are probably some 

 that are even of less size. 

 !N"ot only do the cells in 

 different kinds of plants 

 vary greatly in size, but 

 such variation is also 

 found in different parts 

 of the same plant. It is 

 also known that the cells 

 of a rapidly - growing, 

 healthy plant are larger 

 than those of one that is 

 feeble and sickly. In 

 form, cells vary from the 

 simple globule of the yeast 

 plant in every conceiv- 

 able direction, frequently assuming intricate geometrical 

 figures, the ellipsoidal apparently springing from the 

 spherical; following upward we find the cube, prismatic, 

 hexagonal, stellate, fusiform, and branching cells. The 

 spherical, oval and elliptical are most common in fungi 

 and herbaceous plants, the more complicated appearing 

 in shrubs, trees and other plants belonging to what are 

 termed the higher orders. 



Geowth of Cells, — ^Bach individual cell is a direct 



rig. 3.— WOOD CELLS. 



