GERMINATION. 



361 



idity of the action and the amount of effect are usually 

 far less than that exhibited by the so-called diastase. 



It must not be forgotten, however, that in all cases in 

 which the conversion of starch into dextrin and sugar ia 

 accomplished artificially, an elevated temperature is re- 

 quired, whereas, in the natural process, as shown in the 

 germinating seed, the change goes on at ordinary or even 

 low temperatures. 



It is generally taught that oxygen, acting on the albu- 

 minoids in presence of water, and within a certain range 

 of temperature, induces the decomposition which confers 

 on them the power in question. 



The necessity for oxygen in the act of germination has 

 been thus accounted for, as needful to the solution of 

 the starch, etc., of the cotyledons. 



This may be true at first, but, as we shall presently see, 

 the chief action of oxygen is probably of another kind. 



How diastase or other similar substances accomplish 

 the change in question is not certainly known. 



Soluble Starch. The conversion of starch into 

 sugar and dextrin is thus in a sense explained. This is 



not, however, the only change 

 of which starch is suscepti- 

 ble. In the bean (Phaseol- 

 us multiflorus) Sachs (Sitz- 

 ungsberichte der Wiener 

 Akad., XXXVII, 57) in- 

 forms us that the starch of 

 the cotyledons is dissolved, 

 passes into the seedling, and 

 reappears (in part, at least) 

 as starch, without conver- 

 sion into dextrin or sugar, 

 as these substances do not appear in the cotyledons during 

 any period of germination, except in small quantity near 

 $e joining of #M? seedling, Compare p, 3, 



Fig. 65. 



