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\VIIV IM.ANTy (iKOW, 



271. Some Forms and Changes of Vegetable Matter, ft may l)o usod at once, or it 



may b(> storrd up until it is waiitctl. In annual h(M-l).s, as already explainctl 

 (6S)," in'arly all of it is used for ^'rowtli or for Mossoinin^, as fast as it is inatU*. 

 In bii'nnials, liko tlio Brd, ("arrot, and 'I'ui-nip (70), a ^r»'at part of it is stored 

 up sonicu InMc, ^eniMally in tlu^ loot, and used the tu'xt year. In such perennials 

 us (h(^ i'olato, a part is laid up in the tubers (which are all of the plant that 

 survives the winter), to liej^'in a vi<,'orous ^'rowth tht* next season. In shrubs 

 and trees a part is annually deposited in the newest wood and bark, to bo used 

 for (levelopin<,' tlu^ buds the next spring', in all, a portion is deposited, as we 

 know, sonietiuies in tlu^ fiuit, always in the seed, for tho use of the embryo or 

 new plant, at the be;,'innin^ of its ^'lowth. 



272. W'luMi ve<,'etal)le matter is laid up for futui'o use, a lar^'e part of it is 

 generally in the form of starch. Nearly tlm whole l>ulk of u |)()tato, or of a 

 grain of corn, is starch. This consists of little ;^'rains which aie like mucilage 

 solidified, and they may bo turned into mucila<^e a<;ain. When the plant takes 

 lip a deposit of starch into its system, as fast as it dissolves it in the sap it gene- 

 rally changes it into sugar. Mucilage, starch, sugai', and plant-fabi-ic, all have 

 the same chemical composition, or very nearly; and the ))lant readily changes 

 one into the other as it needs. Notice the changes of vegetal)le matter in a plant 

 of Indian (.'orn. In the leaves, where it is made, the elaborated sap is in tho 

 form of mucilage; in the t<talk, at flowei'ing-time, while on its way to form and 

 nourish the blossoms and grains, it turns sweet, being changed into sugar ; in tho 

 grain, a pai-t is changed intostai'ch and laid up there : when the gi'ain germinates, 

 the starch is dissolved and changed back into sugar ; and in the growing plantlet 

 which it nourishes, the sugar is at lengfh changed into plant -fabric. 



273. Circulation or Conveyance of Elaborated Sap, or Dissolved Vegetable Matter. The new- 



mfule vegetable matter rari'ly accumulates in the leaves where it is made, except 

 in the Century-plant, llouseleek (Fig. 65), and othei- He.shy-leaved ])lants. It is 

 generally distiibuted through all the plant (that is, through all its living ])arts), 

 or carried especially to where a stock is to be laid uj), or where growth is taking 

 place. So the elaboiated 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 generally, — and a part of what descends finds its way even to the ends 

 of the roots, and is all along dilVused laterally into the stem, where it meets and 

 mingles with the ascending crude sap or raw material. Ho there is no separate 



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