NUTRITION AND GROWTH OF PLANTS. 129 



mode of transformation can also be effected by 

 gluten, although it requires a longer time. Seeds, 

 which have germinated, 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 converted 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 formation of the first organs of the 

 young plant, and disappears with the sugar ; dia- 

 stase contains nitrogen and furnishes the elements 

 of vegetable albumen. 



Carbonic acid, water, and ammonia, are the food 

 of fully- developed plants ; starch, sugar, and gum, 

 serve, when accompanied by an azotised substance, 

 to sustain the embryo, until its first organs of nu- 

 trition are unfolded. The nutrition of a foetus and 

 development of an egg proceed in a totally different 

 manner from that of an animal which is separated 

 from its parent ; the exclusion of air does not en^ 

 danger the life of the foetus, but would certainly 

 cause the death of the independent animal. In the 

 same manner, pure water is more advantageous to 

 the growth of a young plant, than that containing car- 

 bonic acid, but after a month the reverse is the case. 



The formation of sugar in maple-trees does not 

 take place in the roots, but in the woody substance 

 of the stem. The quantity of sugar in the sap 



augments until it reaches a certain height in the 



K 



