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A GRAIN OF BARLEY. 103 
himself by M. Aimé Girard,* a well-known French chemist. 
The result of these experiments is to show very conclusively 
that the nitrogenous substances in the aleurone-cells of wheat 
are digestible by man to a very small extent only. We may 
consequently continue to enjoy our white bread without any 
pangs of conscience, and may be content to leave the bran 
to the lower animals who, with their stronger digestive organs, 
are able to make a great deal better use of it than it is 
possible for us to do, 
To return once more to our grain of barley. We must not 
lose sight of the fact that the primary object in view in 
storing up the starch and proteids in the grain is, not to 
afford to man the material for his bread and beer, but to give 
sustenance to the embryonic plant, until it can get its head 
above the ground and look after itself. 
Most of the higher plants, all of those in fact which have 
a green colour, obtain the carbon which forms such an im- 
portant part of their dry substance, from the carbonic acid of 
the air. This carbonic acid, which only amounts to about 
3 parts per 10,000 of air, is decomposed in the green portions 
of the plants, oxygen being evolved and the carbon retained 
in combination with the elements of water. This assimilation 
of carbon is brought about in the tissues of the plants only 
under the action of //gh¢, and the chemical processes involved 
require the presence of a particular substance, chlorophyll, 
which exists in all green plants. We may take it for certain 
that those plants which are not green, that is which contain 
no chlorophyll, are incapable of assimilating carbon from the 
atmosphere. We know, however, that there are many plants 
such as fungi, and even a few of the higher plants, which 
do not contain any chlorophyll, and yet are capable under 
favourable circumstances of vigorous growth. We find on 
close examination that such plants, incapable as they are of 
using directly the carbonic acid of the air, grow either upon 
* Composition Chimique et Valeur Alimentaire des diverses parties 
du grain de Froment. (Ann. Chim. Phys. (6) Vol. 3, p. 289, 1884-) 
