354 HOW CBOPS OKOW. 



tides of water or of otlier liquid matters which thus per- 

 meate the cells. 



§3. 



/ THE VEGETABLE TISSUES. 



• 



As already stated, the cells of the higher kinds of 

 plants are united together more or less firmly, and thus 

 constitute what are known as Vegetable Tissues. Of 

 these, a large number have been distinguished by vege- 

 table anatomists, the distinctions being based either on 

 peculiarities of form or of function. For our purposes 

 it will be necessary to define but a few varieties, viz.: 

 Cellular Tissue, Wood-Tissue, Bast-Tissue and Vas- 

 cular Tissue. 



Cellular Tissue, or Parenchyma, is the simplest of 

 all, being a mere aggregation of globular or polyhedral 

 cells whose walls are in close adhesion, and whose juices 

 commingle more or less in virtue of this -connection. 

 Cellular tissue is the groundwork of all vegetable struc- 

 ture, being the only form of tissue in the simpler kinds 

 of plants, and that out of which all the other tissues are 

 developed. 



Prosenchyma is a name applied to all tissues composed 

 of elongated cells, like those of wood and bast. Paren- 

 chyma and prosenchyma insensibly shade into each 

 other. 



Wood-Tissue, in its simplest form, consists of 

 cells that are several or many tiroes as long as they arc 

 broad, and that taper at each end to a point. These 

 spindle-shaped cells cohere firmly together by their sides, 

 and "break joints "by overlapping each other, in this 

 way forming the tough fibers of wood. Wood-cells are 

 often more or less thickened in their walls by depositions 

 of cellulose »nd other matters, according to their age 



