142 



VEGETABLE FABRIC. 



[LESSON 23. 



of the cells in number. It is by the latter, of course, that the prin- 

 cipal increase of plants in bulk takes place. 



LESSON XXIII. 



VEGETABLE FABRIC I CELLULAR TISSUE. 



391. Organic Structure, A mineral such as a crystal of spar, or 

 a piece of marble may be divided into smaller and still smaller 

 pieces, and yet the minutest portion that can be seen with the mi- 

 croscope will have all the characters of the larger body, and be 

 capable of still further subdivision, if we had the means of doing it, 

 into just such particles, only of smaller size. A plant may also be 

 divided into a number of similar parts : first into branches ; then 

 each branch or stem, into joints or similar parts (34), each with its 

 leaf or pair of leaves. But if we divide these into pieces, the pieces 

 are not all alike, nor have they separately the properties of the 

 whole ; they are not whole things, but fragments or slices. 



392. If now, under the microscope, we subdivide a leaf, or a piece 

 of stem or root, we come down in the same way to the set of similar 

 things it is made of, to cavities with closed walls, to Cells., as we 

 call them (386), essentially the same everywhere, however they may 

 vary in shape. These are the units, or the elements of which every 

 part consists ; and it is their growth and their multiplication which 



FIG. 340. View of a little cellular tissue of a rootlet, cut crosswise and lengthwise. 



