2 TISSUES. 



4. Fibre is a thread-like substance of an excessively 

 small diameter, more generally cylindrical in develop- 

 ment than otherwise, and void of colour, and un- 

 doubtedly often branched or divided, though it is denied 

 by some ; it occurs with membrane in which no fibrous 

 structure can be detected, though often seen inde- 

 pendently of it. 



5. All the elementary structures of plants have their 

 origin in one or other, or both of these two elements ; 

 and may be divided into the cellular, fibrous, and vascular 

 tissues. 



CHAPTER II. 



TISSUES. 



Cellular Tissue. 



6. Cellular tissue is the most generally diffused form 

 of elementary structure throughout the vegetable king- 

 dom, entering greatly into the composition of the more 

 highly developed individuals, and of those far down in 

 the scale, being the sole constituting substance. 



7 . Cellular tissue is both membranous and fibrous, but 

 the membranous form is by far the more common. 

 This form existing in the state of pith is the most suit- 

 Fig. I . a ble for examination, and presents the 



appearance of a number of cellules in 

 close approximation with each other ; 

 the cellules being generally of an hex- 

 agonal shape, and separated from each 

 other by the union of their walls. 

 fi~ The walls of cellular tissue are there- 

 fore composed of two layers, and there 



are no visible means of communication through these 



separating media from cellule to cellule. 



8. The walls of a single cellule, though often very 



