16 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE. 
are gorged not only with their own products of conversion but with 
those of the cells lying beyond them. 
As must be evident frem the writers’ opposition to the theories of 
self-digestion and of aleurone activity, their investigations have been 
overwhelmingly in favor of placing the entire function of diastase 
secretion during germination upon the scutellum. Morphological 
examinations have been made of thousands of barley grains at all 
stages of germination. These have been repeated with a large num- 
ber of varieties and types of barleys grown under varying conditions 
in America and of seed imported from all parts of the world. In all 
cases, the dissolution of the endosperm is effected in the same manner. 
The corrosion commences with the parts directly in contact with the 
scutellum. The action begins as quickly in front of the cells in the 
center of the scutellum as it does in those next to its periphery and 
therefore in juxtaposition to the aleurone layer. All later action is 
such as would occur if the scutellum were the only source of diastase. 
A grain from which the aleurone layer is removed is converted in the 
usual manner. Moreover, the very appearance of the scutellum is 
convincing. On its surface is the epithelial layer, which is typically 
glandular. There are in plant growth no tissues that closely resemble 
specialized secreting tissues, and seldom is there a more unmistakable 
development of this than the epithelial layer, as shown in Plate V, 
figure 1. 
Most investigators have recognized the secreting power of the 
scutellum; indeed, none have denied such function, even when 
attributing to it only a subsidiary activity. Numerous experiments 
have been made in the past and many of them repeated by the 
writers. A grain from which the embryo is removed will not show 
any tendency to germination, even though all external conditions, 
such as light, heat, and moisture be made favorable and ample pro- 
vision for the removal of conversion products be made. On the other 
hand, and under proper artificial conditions, the scutellum is able to 
support itself and to supply food for the growth of the plumule and 
radicle independent of the endosperm. Morris and Brown, Hansteen, 
Pfeffer, and numerous others have shown the ability of the embryo 
(with the scutellum) to digest the starch supplied toit. This has been 
demonstrated in numerous ways. The starch has been furnished in 
the form of macerated endosperm and in the form of a mixture of 
starch and plaster. In every case, the scutellum was able to corrode 
the material supplied and to promote a considerable growth in the 
plantlet. The embryo is also able to utilize an endosperm which is 
entirely without living protoplasm. An excised embryo from a 
healthy, vital grain can be grafted upon a dead endosperm with per 
fect success. Such endosperm may be prepared in any way desired, 
even by prolonged soaking in absolute alcohol; that is to say, after 
