MORPHOLOGY OF THE BOOT. 



31 



through the winter, flower and seed in spring, and perish in 

 early summer. These ma}- be termed WINTER ANNUALS. 



53. Biennials are plants which, springing from the seed and 

 vegetating in one season, live through the interruption of winter, 

 and blossom, fructify, and perish in the next growing season ; 

 their life being thus divided into two stages, the first of vegeta- 

 tion, the second of fructification. In typical biennials, nearly 

 the whole work of vegetation is accomplished in the first stage, 

 with the result of accumulation of a stock of nutritive matter, 

 to be expended in the second stage in the production of blossom 

 and seed. This accumulation is usually stored in the root or in 

 the base of a very short stem in connection with the root. The 

 root of a biennial accordingly enlarges and becomes fleshy, or 

 obese, as this matter accumulates. At the close of the growing 

 season, the leaves perishing and the 

 stem having remained very short (with 

 undeveloped internodes) , the root, 

 crowned with the bud or buds, contains 

 the main result of the summer's work, 

 AS provision for the next year's devel- 

 opment and the completion of the 

 cycle. This development, being thus 

 amply provided for, is undertaken in 

 spring with great vigor ; blossom, fruit, 

 and seed are rapidly produced ; and 

 the stock being consumed, but not at 

 all replenished, the cells of the great 

 root are now empty and effete, and 

 the individual perishes. The Beet, 

 Turnip, Parsnip, and Carrot are fa- 

 miliar examples of biennials, with the 

 store of nourishment in the root. 1 

 The Kohl-rabi is a biennial with this deposit in the stem : 

 the Cabbage, partly in the stem, partly in the head of leaves. 



1 In these the caulicle enlarges with the root, so that the upper anil 

 bud-bearing end is stem. 



Tap-roots of this kind are said, in descriptive botany, to be 



Fusiform or Spindle-shaped, when broader in the middle and tapering 

 towards both ends, as in the common Radish (Fig. 67); 



Conical, when tapering regularly from base to tip, as in carrots, &c. ; 



Napiform, i. e. Turnip-shaped, when the thickened part is wider than high, &c. 



Fascicled Roots are those which form in clusters ; these may be slender or 

 thickened. When much thickened, either irregularly or not of the above 

 shapes, they are said to be tuberous. 



FIG. 67. Radish: a fusiform tap-root 



