n8 SCIENCE PROGRESS. 



formed by weak organic acids into such proteids as are 

 found in the aleurone. On the other hand, even if weak 

 acids in the cell could cause a precipitation from the solu- 

 tion of the proteids in the second suggested condition, it is 

 extremely unlikely that such solutions could pass readily 

 from cell to cell, as must be the case for the accumulation 

 of the aleurone grains. The hypothesis of protoplasmic 

 secretion has much more to be said in its favour. It 

 agrees with the way in which carbohydrate formation 

 takes place, the latter being always the result of the work 

 of a plastid or of protoplasm itself, as we shall see later. 

 It explains also the large amount deposited, as the con- 

 structive activity of the living substance is at the time 

 considerable. 



Taking this view there are two modes again of regard- 

 ing the process. The living substance may deposit it as 

 a definite secretion from its own substance just as the pro- 

 toplasm of other cells may deposit enzymes and other sub- 

 stances, or it may transform into proteid bodies other 

 materials sent to the cells which, though not proteid, never- 

 theless are substances on the way to become so. That is, 

 that the process of proteid construction, normally occurring 

 in the leaves, may also take place in the reservoirs just as 

 in the case of carbohydrates. This is a probable view, and 

 is supported by the fact that when aleurone grain forma- 

 tion is beginning, amide bodies, and particularly asparagin 

 and leucin and sometimes tyrosin, can be shown to be pre- 

 sent in the cells. We know from other experiments that 

 when the aleurone is being used in constructive processes 

 during the germination of the seed such amides do appear 

 as the result of the decompositions accompanying germina- 

 tion. Indeed, these bodies appear from many considera- 

 tions to be the form in which the transport of nitrogenous 

 nutritive material takes place in the plant. Their occur- 

 rence in the cells, therefore, while deposition of aleurone 

 is taking place, indicates them as a probable immediate 

 antecedent of the grains themselves. If this is so, then 

 we must take the view of protoplasmic construction and 

 not mechanical deposition, as we are not able, apart from 



