128 THE ART OP CULTURE. 



vey these substances through the roots, the vital 

 functions of the leaves must cease, and if the pro- 

 cess of assimilation cannot take another form, 

 the plant must die. 



Other substances must be present in a plant, be- 

 sides the starch, sugar, and gum, if these are to take 

 part in the development of the germ, leaves, and first 

 radicle fibres. There is no doubt that a grain of 

 wheat contains within itself the component parts 

 of the germ and of the radi'cle fibres, and we 

 must suppose, exactly in the proportion necessary 

 for their formation. These component parts are 

 starch and gluten ; and it is evident that neither 

 of them alone, but that both simultaneously 

 assist in the formation of the root, for they both 

 suffer changes under the action of air, moisture, 

 and a suitable temperature. The starch is con- 

 verted into sugar, and the gluten also assumes a 

 new form, and both acquire the capability of being 

 dissolved in water, and of thus being conveyed 

 to every part of the plant. Both the starch and the 

 gum are completely consumed in the formation 

 of the first part of the roots and leaves ; an excess 

 of either could not be used in the formation of 

 leaves, or in any other way. 



The conversion of starch into sugar during the 

 germination of grain is ascribed to a vegetable 

 principle called diastase, which is generated during 

 the act of commencing germination. But this 



