THE MALE FEKN 



151 



tion of a further advance whereby plant-life, originally 

 aquatic, has become adapted to terrestrial conditions. 



We have already referred to the existence of true 

 conducting, or vascular, tissues in the Pteridophytes, 

 and these are well seen in the sporophyte of the Male 

 Fern. In the young sporo- 

 phyte this tissue is represented 

 in the stem by a central 

 cylinder, called a stele, but as 

 the plant advances this central 

 stele gives rise to a branching 

 network of steles, as shown in 

 Fig. 48, with steles branching 

 into the leaves. These vas- 

 cular strands are woody; they 

 strengthen the plant so that 

 it may preserve a degree of 

 upright dignity ; and it is along 

 their channels that water with 

 dissolved mineral salts, ab- 

 sorbed by root hairs, is con- 

 ducted throughout the plant, ^o,. 48.— Vascular System 



1 -J. • xi T- OF Male Fben. Enlarged. 



and, moreover, it is through ^ ,. 



" s«, Leading steles of stem ; l.g., 



them that the products of leaf-gap corresponding to 



plant chemistry pass to parts insertion of a leaf; t, steles 



, , • 1 mi branching into leaf. 



where they are required, ihe 



entire plant may be likened to a house of many 

 rooms, with water " laid on " in every apartment, 

 and in which there is a system of communication of 

 the parts with the whole. The " house " is occupied 

 by myriads of microscopic protoplasts with definite 

 occupations. Moreover, there is a system of venti- 



