114 



THE BIOLOGY OF A PLANT. 



ground bounded by a black margin (the epidermis) 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 



ep 



fp 



s.p 



spro 



. 48. Cross-section of the rhizome of Ptcris. l.r, lateral ridges; f.p, fundamental 

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

 fibro-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 fundamental system consists in Pteris of three tissues : 



(a) fit i!n mental parenchyma (Fig. 48, f.p\ the soft whitish 

 mass forming the principal substance of the rhizome ; 



(b) sclerotic parenchyma (s.p), the brown hard tissue lying 

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

 able ; 



(c) sclerotic prosenchyma (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. 



