126 GAGER: GLANDS IN THE EMBRYO OF ZEA 
A discussion of the various interpretations that have been given 
since the time of Gaertner as to the homology of its parts, would 
not be germane to this paper.* Goebel,** in 1895 and 1900 on 
the basis of Bruns’s? work and of his own study of Streptochaeta, 
interprets it as a true cotyledon, while “the epiblast, which lies 
over against it, but is not present in all grasses, is an arrested 
leaf,” and the coleoptile, or sheath of the plumule, is the third leaf. 
The first green leaf is the fourth leaf of the plant. Thus the view 
most generally held at the present time closely agrees with that 
put forward by Malpighi in 1675. 
Questions of function have been fully as puzzling as those of 
structure, if not more so, and this, too, notwithstanding the oppor 
tunities for solution by the method of experiment. 
As early as 1845, Schleiden ® regarded the scutellum of the 
oat as an organ of absorption, and was followed in this view by 
Schacht * and Sachs." It was Sachs who first pointed out the 
fact that the embryo, in its earlier stages of development, lives as 
a parasite on the endosperm, and we owe to him the term 
“absorptive epithelium,” as applied to the outer layer of cells of 
the scutellum. 
Three principal regions are concerned in the nourishing of the 
germinating embryo. These are the scutellar epithelium, the 
aleurone layer, and the remaining cells of the endosperm. 
‘Dutrochet had shown that starch, as such, could not pass 
through semi-permeable membranes, like the cell-walls of plants, 
by osmosis, and thus the conclusion was forced that the food 
stored in the endosperm must be transformed before it could 
become available to the awakened embryo. 
The earliest idea to develop in this connection was th 
effective agent in this transformation was gluten. Fabroni, in I 785» 
is said + to have isolated from grape-juice a gluten-like, adhesive 
matter, without which fermentation did not take place. Thenard,? 
experimenting with several fruits, confirmed Fabroni’s experiment, 
and considered the glutinous matter, isolated by filtering fruit 
juices, as identical with yeast. Thus the attention of a 
oe physiologists was naturally directed to gluten as indicated 
above. 
at the 
ee os. 
*The different theories have been discussed by Van Tieghem. '” i, 12 
t Cited by Thomson 5 (1818), page 291. 
