130 GAGER: GLANDS IN THE EMBRYO OF ZEA 
the aleurone layer. This view is stated by Pfeffer, *’ in 1900, 
(page 599), who calls the diastase secreted by the scutellum ‘“ac- 
cessory diastase,” and says its secretion may always be regulated 
by the needs of the plant. This conclusion is based in part upon 
the experimental demonstration that isolated bits of endosperm 
placed in contact with water become spontaneously depleted. In | 
these experiments, the disappearance of the starch proceeds cen- 
tripetally from the surface of the endosperm in contact with the 
water. 
5. All storage tissues are capable of auto-depletion, according 
to Puriewitsch.“* This conclusion was based upon studies of the 
endosperm and cotyledons of various seeds, and the contents of 
roots, bulbs, rhizomes, tubers, and other stems. In 1896 Griiss” 
states that ‘‘It is well known that the endosperm cells themselves 
secrete a ferment during germination” (pages 408, 422). . This; 
together with his paper of 1895, indicates that his position then 
should be classed here, but in 1897 (page 664) he says: «‘ Seed- 
lings fram which one has taken the endosperm may, without the 
aid of bacteria, nourish themselves upon starch paste, which there- 
by becomes changed to sugar.’’ This, however, does not neces- 
sarily imply a change from his preceding position. 
In addition to the above views, may be mentioned that of Wig- 
and,” who in 1888, attributed a diastatic function to the aleurone 
layer, but only through the mediation of bacteria developing in 
it; and Hansteen’s,” founded upon extensive though insufficiently 
guarded experiments, that it is not necessary for diastase to pro- 
ceed from the scutellum during germination. 
In 1890, Haberlandt”® stated (page 48) that ‘‘ The aleurone 
layer of the grass-endosperm, and presumably also of seeds of 
other plants, is henceforth to be classed with the digestive glands 
of insectivorous plants,” and in 1904 he states (page 477) that 
“its histological structure, in connection with the experimental 
fact that the isolated gluten layer richly secretes diastase, forms 
the ground for my notion concerning the function of that layer.” 
It is interesting to note that, in this last mentioned work, the 
pendulum has swung back to the original idea, advanced by Kirch- 
hoff ninety years previously, that in germinating seeds the gluten 
is a source of the agent that changes starch to sugar. It hardly 
seems probable that Haberlandt’s view will finally stand. 
