72 THE LIFE OF THE PLANT 



which the nutrition of the cell was explained in our last 

 lecture. This parallel might, indeed, have been ex- 

 pected, since the life of the embryo is the sum of the 

 life of the cells which compose it. 



We have now proved that during the process of 

 germination matter is only translocated from one organ 

 to another within the seed. Notwithstanding the 

 apparent increase in size and the growth of the young 

 plant, we can prove by weighing the seed and the seedling 

 that no increase in substance really takes place during 

 this period. Simple weighing would, however, be 

 insufficient for the purpose ; if we record the weight 

 first of the seed and then of the seedling developed from 

 it, we certainly do notice that the latter is heavier than 

 the former ; but this is easily explained. We have seen 

 that different parts of a plant contain very different 

 quantities of water : seeds scarcely contain any water, 

 while the plant as a whole contains a considerable 

 quantity.^ During germination water is absorbed first 

 by the whole seed and eventually by the rootlet, a fact 

 which explains the addition in weight. If, on the other 

 hand, we had dried both the seed and the seedling at a 

 temperature of ioo°, and determined their weight in a 

 dry state, we should have found that the plant has lost 

 in dry weight during the process of germination, although 

 it has increased in size. The question arises : what 

 has become of the lost substance ? As a rule we do not 

 notice any excretion by plants of dry or liquid matter 

 such as takes place in animals, and even if there were 

 any such excretion, having taken it into consideration, 

 we should still find that the whole of the loss in weight 

 was not by any means accounted for. We can only 

 conclude that the seed loses some of its substance in 

 the form of gaseous products which disappear into the 

 air. 



1 See table of analysis on p. 43. 



