136 THE ART OF CULTURE. 



stances through the roots, the vital functions of the 

 leaves must cease, and if the process 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 radicle fibres, and, we must sup- 

 pose, 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 converted into sugar, and the gluten 

 also assumes a new form, and both acquire the capa- 

 bility 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 forma- 

 tion of the first part of the roots and leaves ; an ex- 

 cess 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 princi- 

 ple called diastase, which is generated during the act 

 of commencing germination. But this mode of trans- 

 formation can also be effected by gluten, although it 

 requires a longer time. Seeds, which have germin- 

 ated, always contain much more diastase than is 

 necessary for the conversion of their starch into 

 sugar, for five parts by weight of starch can be con- 

 verted into sugar by one part of malted barley. 

 This excess of diastase can by no means be regarded 

 as accidental, for, like the starch, it aids in the form- 

 ation of the first organs of the young plant, and dis- 

 appears with the sugar ; diastase contains nitrogen 

 and furnishes the elements of vegetable albumen. 



Carbonic acid, water, and ammonia, are the food 

 of fully-developed plants 3 starch, sugar, and gum. 



