1203 
Embryo and Aleurone Layer of Hordeitm . 
suppression of the secretory functions of the aleurone layer, and are re¬ 
garded as confirmatory of the experimental evidence furnished by direct 
examination of the secretory functions of the isolated aleurone layer. 
In short, endospermic depletion, as it occurs in the intact seed, is 
principally conditioned by the action of enzymes secreted by the aleurone 
layer and embryo; in the isolated endosperm, by the aleurone-layer 
secretions, and in both cases the principal role is due to the aleurone layer ; 
the amyloclastic enzyme pre-existent in the inner endosperm and that 
which it generates is adjunctive. 
4. The amyloclastic enzymes secreted by the embryo and aleurone 
layer are identical, and are distinct from that existent and generated by 
the inner endosperm. 
The columnar epithelial and aleurone-layer cells, although morpho¬ 
logically different, possess similar physiological functions. The view, based 
on this fact, is advanced:—the aleurone layer is the analogue of the 
columnar epithelium, and this analogy suggests that the endosperm of 
Hordeum represents an abortive or undifferentiated embryo, and conse¬ 
quently, on biochemical grounds, the phenomenon of ‘ double fertilization ’ 
or ‘ triple fusion 5 possibly occurs in Hordeum. 
5. Both auto- and papain-digestion of ungerminated barley substance 
lead to considerable augmentation of its amylase content or its amylolytic 
activity over and beyond that which follows on direct digestion. 
Similarly conducted comparative digestion experiments with material 
from intact seeds and with material from seeds placed under germination 
conditions show that— 
(1) The values of the amylase content of intact seeds as determined 
by the three methods of digestion tend to converge as the period 
of germination advances. 
(2) The values of the amylase content of parts of the seed as determined 
by the three methods of digestion vary. Thus :— 
(a) the embryo throughout gives higher values by direct than by either 
papain- or auto-digestion; 
(b) the aleurone layer at first gives lower and afterwards higher 
values by the direct method of digestion ; 
(c) the inner endosperm throughout gives lower values by the direct 
method, but the divergence of results tends to diminish as 
germination proceeds. 
Examination of the amylase content of the leaf and other organs of 
Tropaeolum by the three methods of digestion shows that the direct method 
invariably yields higher results than either the papain- or auto-digestion 
method. This result implies that in actively functionary tissues as opposed 
to the reserve storage organ of Hordeum , the amylase is present wholly in 
the ‘ active * or ‘ free ’ condition, and further indicates that papain-digestion, 
