STARCH IN GERMINATING PEAS 181 



same whether the seeds were first soaked or not. The solution of 

 the starch began in the naturally peripheral cells. In the internal 

 cells which had been exposed by the mutilation, digestion did not 

 begin at once, but only at about the same time that the cells in 

 the same relative position in the control cotyledons began to show 

 a solution of the starch (fig. 6). In other words, in all cells which 

 have relatively the same position in the cotyledon, solution of 

 the starch occurs at approximately the same time, irrespective of 

 any mutilation of the surface layers. Mutilations causing the 

 internal cells to lie at the surface do not at all hasten the solution 

 of the starch in those cells. In such cases, the cells of the interior, 

 exposed by the mutilation, surely become wetted as soon as the 

 peripheral cells, yet the starch is dissolved first from those cells 

 which are normally peripheral, and only in their proper turn from 

 those normally internal. It seems improbable, therefore, that dif- 

 ferences in the imbibed condition of the different cell layers can 

 play any part in causing the difference in behavior of these' layers 

 in regard to starch digestion. 



While examining the sections obtained from the mutilations of 

 experiment 6, it was noticed that the starch in those cells which 

 had been injured during the mutilation was not at all affected. 

 This suggested that a mechanical injury, which might be supposed 

 to bring about cell death, might prevent the solution of the con- 

 tained starch, even though diastatic digestion progressed vigor- 

 ously in immediately adjoining cells. To acquire more informa- 

 tion on this point, dried peas were soaked in water until imbibition 

 was complete, then the cotyledons were deeply punctured by means 

 of a sterile needle. These peas were allowed to germinate in a moist 

 chamber. Sections made from time to time showed that the solu- 

 tion of the starch proceeded in a quite normal manner except in 

 those cells which had been injured by the needle (fig. 7) . In these 

 cells, the starch persisted in its original condition, even until the 

 remainder of the cotyledon had been completely deprived of this 

 substance. This lack of the solution of the starch can hardly be 

 due to the mere killing of the cells, for in experiments 1 and 5 

 the cells were surely killed during the grinding, yet in these, the 

 enzymotic activity began as soon as water was added. 



