22 STRUCTURE AND PROPERTIES 



14. Two grand classes are obvious on con- 

 sidering the foregoing organography, viz. Cellu- 

 lar and Vascular plants. The first being wholly 

 composed of cellular tissue, the last of both 

 cellular tissue and vessels. Vascular plants 

 may again be divided into two principal kinds 

 those whose vessels and cells extend longitudi- 

 nally, and whose growth takes place towards the 

 centre of the stem ; which from this circumstance 

 have been termed Endogenous : * and, secondly, 

 those which have vessels or bundles of elongated 

 cells, taking either a longitudinal or transverse 

 direction, and in which the growth is always 

 towards the circumference of the stem these 

 are called Exogenous.-f- 



15. Having shewn what the general structure 

 of plants is composed of, without reference to 

 those particular organs on which their growth, 

 nourishment, and reproduction depend, it may 

 here be desirable to give some idea of the pro- 

 perties inherent in vegetable tissue, before the 

 organs, which are modifications of that tissue, 

 and of course partake of its properties, are more 

 especially noticed. 



Organized beings are, like all other bodies, 



* From tvov, within, and jiyvofiai, to produce. 

 t From iu>, without, and ytyvo/eu. 



