114 



THE BIOLOGY OF A PLANT. 



pround bounded bj a black margin (the epidermii) and marked 

 by various colored or pale spots and bands ; the latter are differ- 

 ent tissues, or systems of tissue. These different structures are 

 arranged in three groups or systems of tissue^ which are found 



spro 



Fig. 48.— Cross-section of the rhizome of Pteris. Lr, lateral ridges; /.p, fundamental 

 parenchyma; s.p, sclerotic parenchyma; s.pro, sclerotic prosenchyma; /.b, x 

 flbro-vascular bundles. 



among all higher plants in essentially the same form, though 

 differing widely in the minor details of their arrangement. 

 These are : — 



I. The Fundamental System of Tissues. 

 II. The Epidermal System. 

 III. The Fibro-vascular System. 



The Fundmnental system consists in Pteris of three tissues : 



(ci) fimdainental parenchyma (Fig. 4:8,y.j9), the soft whitish 

 mass forming the principal substance of the rhizome ; 



(5) sclerotic parenchym^a (s.p), the brown hard tissue lying 

 just below the epidermis, from which it is scarcely distinguish- 

 able; 



(c) sclerotic prosencJiym^a (s.pro), black or reddish dots and 

 bands of extremely hard tissue, most of which is contained in two 

 conspicuous bands lying one on either side of a plane joining 

 the lateral ridges. 



