ENDOGENS. 



thorny when wild are not so under cultivation. 

 Thorns differ from prickles, which are hardened 



hairs. 



8. Lewes are constituted of cells, with cavities, 

 fibro-vascular bundles, and epidermis. (Fig. 27.) 



Fig. 27. 



The veins in a leaf are the vascular parts, and their 

 distribution differs in the types of Endogens and 

 Exogens, so as to afford a ready means of discrimina- 

 tion. The veins in the leaves of Endogens are gen- 

 erally parallel or straight, and do not form a network 

 as in Exogens. (Fig. 28.) 



When two leaves are at the same level, one on each 

 side of the stem, they are called opposite; when a 

 circle of leaves is thus produced it is called a whorl. 

 When there is only one leaf on the same level the 



