LESSON 22.] 



GROWTH OF THE PLANTLET. 



141 



388. The Growlh of the Plantlet when it spTings from the seed is 

 only a continuation of the same process. The bladder-Hke cells of 

 which the embryo consists multiply in number by the repeated 

 division of each cell into two. And the plantlet is merely the ag- 

 gregation of a vastly larger number of these cells. This may be 

 clearly ascertained by magnifying any part of a young plantlet. The 

 young root, being more transparent 

 than the rest, answers the purpose 

 best. Fig. 56, on page 30, repre- 

 sents the end of the rootlet of Fig. 

 55, magnified enough to show the 

 cells that form the surface. Fig. 

 337 and 338 are two small bits of 

 the surface more highly magnified, 

 showing the cells still larger. And 

 if we make a thin slice through the 

 young root both lengthwise and 

 crosswise, and view it under a good 

 microscope ^Tfig. 340), we may per- 

 ceive that the whole interior is made up of just such cells. It is 

 the same with the young stem and the leaves (Fig. 355, 357). 

 It is essentially the same in the full-grown herb and the tree. 



389. So the plant is an aggregation of countless millions of little 

 vesicles, or cells (Fig. 339), as they are called, essentially like 



the cell it began with in the formation of the embryo 

 (Fig. 329) ; and this first cell is the foundation of 

 the whole structure, or the ancestor of all the rest. 

 And a plant is a kind of structure built up of these 

 individual cells, something as a house is built of 

 bricks, — only the bricks or cells are not brought to the forming 

 plant, but are made in it and by it ; or, to give a better comparison, 

 the plant is constructed much as a honeycomb is built up of cells, 

 — only the plant constructs itself, and shapes its own materials into 

 fitting forms. 



390. And vegetable growth consists of two things ; — 1st, the ex- 

 pansion of each cell until it gets its full size, (which is commonly not 

 more than j^g^ of an inch in diameter) ; and 2d, the multiplication 



FIG, 337- Tissue from the rootlet of a seedliog Maple, magnified, showing root-haira 

 ^. A small portion, inoi^'magnified. ' 

 FIG. 839. A regularly ttrelre-sided cell, like those of lig. 340, detached. 



