322 HOW CROPS GROW. 
germinating seed, the change goes on at ordinary or even 
low temperatures. 
It is generally taught that oxygen acting on the album- - 
inoids 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, ete., 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, how- 
ever, the only change of 
which starch is susceptible. 
In the bean, (Phaseolus 
multiflorus), Sachs (Sitz- 
ungsberichte der Wiener 
Akad., XXXVII, 57) in- 
forms us that tle 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 germina- 
tion, except in small quantity near the joining of the 
seedling. Compare p. 64, Unorganized Starch. 
The same authority gives the following account of 
the microscopic changes observed in the starch-grains 
themselves, as they undergo solution. The starch-grains 
of the bean have a narrow interior cavity, (as seen in 
fiz. 65, 1.) This at first becomes filled with a liquid. 
> 
Fig. 65. 
