MORPHOLOGY OF THE BARLEY GRAIN. 19 
difference can not be without a purpose, and fortunately this pur- 
pose is easily explained without the necessity of having recourse to 
any theory of secretion. The aleurone layer undoubtedly exercises 
a strong protective function. In rainy weather, fungi are invariably 
to be found investing the barley grain and feeding upon the feebly 
active cells of its envelopes. Their hyphe often run through all the 
investing layers of the seed without bemg able to penetrate the 
aleurone layer. Whether or not it be the vital resistance of its pro- 
toplasm, the mere mechanical obstacle of its heavily cuticularized 
walls, or both, this tissue is an effective barrier to the inroads of 
molds and bacteria. The fact that such protection is of absolute 
necessity is readily appreciated. Within the endosperm is stored the 
food upon which the future development of the embryo is absolutely 
dependent. Even the perpetuation of the species rests upon the 
proper conservation of this reserve food material. This mass of 
readily assimilated compounds is an ideal food for all sorts of sapro- 
phytic and parasitic organisms. It is therefore not surprising to find 
built around this material a specialized tissue with a highly protective 
function. 
The aleurone layer serves a second purpose, but one which alone 
would hardly justify its existence, in that it appears to be more 
opportune than essential. When the plant is first establishing itself 
in the soil, it utilizes the starch endosperm, a material rich in carbo- 
hydrates, which seems to meet all the requirements cf early growth. 
When once its green leaves are exposed, however, photosynthesis is 
able to supply all its needs for starch. With nitrogenous food mate- 
rial the problem is more difficult. A considerable extension of feed- 
ing surface in the roots is necessary before such material can be pro- 
cured in any quantity. The starch endosperm contains an extremely 
limited amount of nitrogenous matter and that stored in the embry- 
onic tissues is soon exhausted. The breaking down of the aleurone 
layer and the utilization of its highly nitrogenous cell contents comes 
at the critical period in the life of the plantlet when this material is 
of especial value. This may account for the extra thickness of this 
layer in certain genera of grasses, of which Hordeum is one of the 
most notable examples. 
GREATER DIASTATIC POWER OF SMALL-BERRIED AND OF HIGH- 
NITROGEN BARLEYS. 
It is interesting to note that the theory of scutellar secretion con- 
forms nicely to an apparently satisfying explanation of a widely rec- 
ognized fact in the utilization of barley malt. Distillers have long 
known that their requirements are best met by a malt of high dia- 
static power and that small-berried barleys of high nitrogen content 
are best adapted to produce such malt. With those brewers who 
are producing a beer in the manufacture of which malt adjuncts, such 
