ROOTS 39 
The first season’s work consists mainly in producing the 
food which is stored in the roots. To such storage is 
due their characteristic fleshy appearance. If this root is 
planted in the following spring, it feeds the rapidly grow- 
ing stem which proceeds from the bud at its summit, and 
an abundant crop of flowers and seed soon follows; while 
the root, if examined in late summer, will be found to be 
withered, with its store of reserve material quite exhausted. 
The roots of the dahlia (Fig. 17), the sweet potato, and a 
multitude of other perennials, or plants which live for many 
years, contain much stored plant-food. Many such plants die 
to the ground at the beginning of winter, and in spring make 
a rapid growth from the materials laid up in the roots. 
50. Extent of the Root-System.—The total length of 
the roots of ordinary plants is much greater than is usually 
supposed. They are so closely packed in the earth that 
only a few of the roots are seen at a time during the 
process of transplanting, and when a plant is pulled or dug 
up in the ordinary way a large part of the whole mass of 
roots is broken off and left behind. A few plants have 
been carefully studied to ascertain’ the total weight and 
length of the roots. Those of winter wheat have been 
found to extend to a depth of seven feet. By weighing 
the whole root-system of a plant and then weighing a 
known length of a root of average diameter, the total 
length of the roots may be estimated. In this way the 
roots of an oat plant have been calculated to measure 
about 154 feet; that is, all the roots, if cut off and strung 
together end to end, would reach that distance. 
51. Absorption of Water by Roots. — Many experiments 
on the cultivation of corn, wheat, oats, beans, peas, and 
other familiar plants in water have proved that some plants, 
