lOO TEXTBOOK OF BOTANY 



one ; and it is not surprising that a large amount of special 

 tissue has been developed for the purpose. 



127. Roots. — Now and then a root arises a short distance 

 back of the growing point of the stem ; other roots grow from 

 the bases of the leaf -stalks. The roots are short and slender ; 

 occasionally they branch. A short portion of each root, just 

 back of its end, bears many root hairs. Each root hair is a 

 surface cell of the root which has grown out beyond its 

 neighbors. These hairs come into very close contact with 

 the particles of soil, and take in some of the water which is 

 always present between and about the soil particles. With 

 the water the root hairs absorb salts and other substances 

 which are dissolved in the soil water and which the fern can 

 use as food. Thus all the materials which come from the 

 soil, including the plant's supply of water, are taken in by the 

 root hairs ; these materials are passed on to the inner cells 

 of the root, finally reaching the vascular bundles whose cells 

 conduct the materials through the root and thence to the stem 

 and leaves. 



128. Leaves. — A leaf begins as a small swelling upon the 

 growing point of a stem or branch. The life of a single leaf 

 covers the greater part of three years. It passes the first 

 two years below ground ; in the spring of the third year it 

 pushes above the surface and unrolls from the base, growing 

 at the tip as it unrolls, until it has reached its full size ; in 

 the fall of the same year it dies, and finally it withers, is 

 broken, and the parts above ground decay. Under ordinary 

 conditions, the leaves grow to be from two to four feet high ; 

 but they may become much larger, and in some countries they 

 reach a height of twelve or fourteen feet. A leaf consists of 

 a slender stalk and a much-divided blade. The central axis 

 of the blade is a continuation of the leaf -stalk and corre- 

 sponds to the midrib of an undivided leaf like that of an oak ; 

 borne upon this central axis are two rows of leaflets. The two 

 lower leaflets are often much larger than the upper ones, and 



