72 



THE BIOLOGY OF A PLANT. 



colored or pale spots and bands ; the latter are different tissues, or 

 systems of tissue. These different structures are arranged in 

 three groups or systems of tissue, which are found among all 



spro 



FIG. 35. Cross-section of the rhizome of Pteri*. l.r, lateral ridges; f.p, fundamenta 

 parenchyma; s.p, sclerotic parenchyma; s. pro, sclerotic prosenchyma; f.b, x, fibro- 

 vascular bundles. 



higher plants in essentially the same form, though differing 

 widely in the minor details of their arrangement. These are : 



I. The Fundamental System. 

 II. The Epidermal System. 

 III. The Fibro-vascular System. 



The Fundamental system consists in Pteris of three tissues : 



(a) fundamental parenchyma (Fig. 35, /*./>), the soft whitish 

 mass forming the principal substance of the rhizome ; 



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

 below the epidermis, from which it is scarcely distinguishable ; 



(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. 



The sclerotic parenchyma and the sclerotic prosenchyma both 



