Embryo and Aleurone Layer of Hordeum. 1149 
readily induced and to exhibit its powers more actively in its dorsal 
portion. 
In the anaerobic series of experiments (Experiments 2, 3, &c.), the 
early suppression and eventual annihilation of the aleurone-layer secretory 
mechanism is obvious from a consideration of the lower amounts 
of reducing sugars present in the media in these experiments ; in fact, 
comparison of the amounts of reducing sugars is a far more accurate 
criterion and measure of the relative depletive capacities possessed by two 
tissues, than is comparison of their amylolytic augmentative capacities. 
As already insisted, the demonstration of this latter capacity, unless it 
can be shown that the amylases derived from the aleurone layer and inner 
endosperm are of equal value in their power of attack upon barley starch 
under normal conditions of germination, loses much of its importance and 
value. 
The objects in these anaerobic experiments retained their original mass 
and form, and there was, as shown by a searching macro- and microscopical 
examination, an almost entire absence of evidence indicative of digestive 
changes. In all, as was to be anticipated, there were examples of eroded 
starch grains, produced no doubt prior to the complete inhibition of the 
secretory functions of the aleurone layer. The characteristic brown colour 
developed invariably in the functioning aleurone layer, especially at its 
exposed margins, was wanting. 
Lastly, although direct digestion of the objects shows the existence 
of small amounts of free amylase, thus pointing to its inactivation or 
destruction as the result of its activity, yet papain-digestion indicates the 
presence of very considerable amounts of ‘ latent’ amylase. The inference 
to be derived from these facts is that the reducing sugars found result from 
the more active aleurone-layer secretion at an early epoch in the course of 
the experiments. 
These series of experiments afford, on the one hand , convincing evidence 
of the effectiveness of the method of sterilization employed; not only did 
the cultures during this lengthy period of experiment remain absolutely 
sterile, but the employment of alcohol in place of CuS 0 4 , as a sterilizing 
agent, obviates the troublesome source of confusion in experiments with 
endosperms to which reference will be made later. On the other hand they 
present an array of experimental data which renders it extremely difficult 
to avoid the conclusion that, during the germination process, starch disso¬ 
lution and digestion (and, as we shall see later, cellulose digestion) are 
largely dominated by exercise by the aleurone-layer cells of their undoubted 
secretory functions. 
