88 WHY PLANTS GROW, 
271. Some Forms and Changes of Vegetable Matter, It may be used at once, or it 
may be stored up until it is wanted. In annual herbs, as already explained (68), 
nearly all of it is used for growth or for blossoming, as fast as it is made. In 
biennials, like the Beet, Carrot, and Turnip (70), a great part of it is stored 
up somewhere, generally in the root, and used the next year. In such perennials 
as the Potato, a part is laid up in the tubers (which are all of the plant that 
survives the winter), to begin a vigorous growth the next season. In shrubs and 
trees a part is annually deposited in the newest wood and bark, to be used for de- 
veloping: the buds the next spring. In all, a portion is deposited, as we know, 
sometimes in the fruit, always in the seed, for the use of the embryo or new plant, 
at the beginning of its growth. 
272. When vegetable matter is laid up for future use, a large part of it is gen- 
erally in the form of starch. Nearly the whole bulk of a potato, or of a grain of 
corn, is starch. This consists of little grains which are like mucilage solidified, and 
they may be turned into mucilage again. When the plant takes up a deposit of 
starch into its system, as fast as it dissolves it in the sap it generally changes it into 
sugar. Mucilage, starch, sugar, and plant-fabric, all have the same chemical com- 
position, or very nearly ; and the plant readily changes one into the other as it needs. 
Notice the changes of vegetable matter in a plant of Indian Corn. In the leaves, 
where it is made, the elaborated sap is in the form of mucilage; in the stalk, at 
flowering-time, while on its way to form and nourish the blossoms and grains, it 
turns sweet, being changed into sugar; in the grain, a part is changed into starch 
and laid up there: when the grain germinates, the starch is dissolved and changed 
back into sugar; and in the growing plantlet which it nourishes, the sugar is at 
length changed into plant-fabric. 
273. Circulation or Conveyance of Elaborated Sap, or Dissolved Vegetable Matter. The 
new-made vegetable matter rarely accumulates in the leaves where it is made, ex- 
cept in the Century-plant, Houseleek (Fig. 65), and other fleshy-leaved plants. 
It is generally distributed through all the plant (that is, through all its living parts), 
or carried especially to where a stock is to be laid up, or where growth is taking 
place. So the elaboratéd sap, passing out of the leaves, is received into the inner 
bark, at least in trees and shrubs,—or in herbs it may descend through the soft 
parts enerally,— and a part of what descends finds its way even to the ends 
of the roots, and is all along diffused laterally into the stem, where it meets 
and mingles with the ascending crude sap or raw material. So there is no separate 
