238 THE SECOND BOOK OF BOTANY. 



EXERCISE LXXIII. 

 Duration of Hoots. 



Roots are divided into classes, according to their 

 duration. 



ANNUAL ROOTS are those which spring from the 

 seed, and die the same year or season. They are 

 always fibrous, arising from numerous divisions of 

 the main or tap root, or, as in all annual grasses, the 

 root is made up entirely of such fibres proceeding at 

 once from the base of the stem. 



BIENNIAL ROOTS are those which live through two 

 seasons, dying at the close of the second. You may 

 trace their history in every garden. Plant parsnip- 

 seeds, for instance, which send down their true roots, 

 and form an abundant crown of showy leaves. In the 

 autumn the leaves die, and the tap-roots, filled with 

 nutritious matters, so valuable to man, survive the 

 winter, and in the following spring begin to grow 

 again. But the course of growth is reversed from 

 that of the previous season. Before, it was busy 

 storing up nourishment, which is now spent in form- 

 ing stem, leaves, flowers, and seeds, with the ripen- 

 ing of which the whole plant dies. 



PERENNIAL ROOTS. These are found in plants 

 which last year after year. In trees and shrubs the 

 same roots live and grow indefinitely ; but in herbs 

 that continue from year to year, the active roots of 

 each season die at its close, leaving a stock of newly- 

 formed roots to perform the work of the succeed- 

 ing seasons. The peony and the horseradish are 

 examples. 



