Embryo and Aleurdne Layer of Hordeum. 1173 
stituted show that the isolated section of the endosperm was unable to 
induce autonomously in any degree the changes just described. 
In order to test this important point, experiments similar to those 
described in mode of preparation and duration were instituted with em¬ 
bryos and aleurone-layer fragments, placed upon endosperm sections 
prepared from seeds which had been previously put in water at 90° C. 
and retained at this temperature for half an hour . Many of these burst 
their integuments, and the starch contents of the sections selected showed 
distinct evidence of partial gelatinization. It is inferred that the pre¬ 
existent enzymes of the ungerminated grain are largely localized, as Ford 
and Guthrie’s investigations show, and my own confirm, in the peripheral 
portions of the endosperm. 1 
The results were in no way opposed to those recorded above ; dis¬ 
solution and digestion of the amyliferous cell walls and starch content 
proceeded to the same extent as in experiments with unboiled sections, 
but the processes were obviously retarded, possibly by either physical or 
chemical changes in the endospermic tissue or both, induced by the agency 
of heat. 2 
These experiments naturally raise the question of what constitutes a 
‘ control ’ ; strictly speaking, in the above experiments what is wanted is 
a section of an endosperm with its enzymes destroyed. Heating, if suf¬ 
ficiently prolonged, certainly accomplishes this, but the possibility of 
introducing new and unfavourable conditions is not precluded, and these 
may seriously inhibit the action of enzymes, such as amylase, cytase, &c. 
The possibility of finding some means whereby self-digestion of the 
inner endosperm may be accomplished without the aid of the active 
secretions of the embryo and aleurone layer is granted, but, so far at least, 
the suggestion rests on a basis which is purely presumptive. The sug¬ 
gestion of Ling that the pre-existent amylase of the resting grain during 
germination is transformed into the amylase of malt, although the possi¬ 
bilities of such a transformation are conceded, is unsupported by experi¬ 
mental evidence, and for the present at least belongs exclusively to the 
domain of theory. 
It is of interest in this present section to refer to certain results 
yielded by earlier attempts to demonstrate the cytoclastic secretory powers 
of the embryo and aleurone layer. 
A series of small Petri dishes, 4 cm. in diameter, each containing the 
gelatine-mineral salt medium, similar to that employed in the ‘ miniature 
1 Finely ground endospermic substance of barley, placed in dry test-tubes heated for half an 
hour in an ordinary Koch’s steamer, annihilates effectively the pre-existent amylase of the un¬ 
germinated grain. 
2 Further light on this subject is afforded by the experimental evidence given in Section XII 
(Inactivation of Amylase). 
