128 GAGER: GLANDS IN THE EMBRYO OF ZEA 
convert into sugar four times its weight of starch. These studies, 
and that of Payen,* in 1824, paved the way for the discovery of 
diastase by Payen and Persoz® in 1833. This substance, its dis- 
coverers announced, could convert into dextrine 2,000 times its 
own weight of starch. 
Later (1843, 1846) Payen* * demonstrated that starch must 
be altered “ by water and diastase” before it can pass through 
cell-walls, and that only after being thus altered can it pass from 
tissue to tissue. The question now became, What is the source 
of the diastase by which, in germination, the endosperm is 
digested ? 
Raspail ® had shown, in 1825, that, in germination, the endo- 
sperm gradually lost its starch, while the enlarging embryo became 
gradually enriched with starch-grains, and, in 1862, Sachs * ob- 
served that, in the germination of grass-embryos, the change of 
starch to sugar “‘ begins on the side of the endosperm which lies 
next to the absorbing scutellum.’’ He also demonstrated that 
the products of the solution of the endosperm are translocated to 
the germ, and homologized the scutellar epithelium “ with the 
organ of the same name on the cotyledons of pans, and with the 
young epidermis of the Ricixws cotyledon . . 
From this time on, beginning with Bloriasewakt sie 1875, 
_ there have followed a number of researches on the germination of 
grass embryos deprived of endosperm, and on the ability of isO- 
lated embryos to utilize artificial endosperm. Among the earlier 
and more extensive of these investigations, are those of Brown 
and Morris,'* '’ who demonstrated in 1888 the possibility of grow- 
ing grass embryos on artificial endosperm, and, in 1890, showed 
that, at the beginning of germination, starch first reappears in the 
cells of the scutellum immediately under the epithelium. Its first 
appearance here, being coincident with the earliest stages of the 
depletion of the endosperm, was taken as evidence that it came 
from the latter. 
The fundamental investigations as to whether or not the dia- 
stase could diffuse through cell-walls and, therefore, would not 
necessarily have to be secreted by the cells where it is to act, was 
not made until 1894, when Griiss,” with results contrary to those 
of Krabbe, in 1890, demonstrated the possibility of such diffusion. 
