: 
} 
ANALYSIS OF THE VEGETATION OF THE GRAMINE. 589 
to become yellow and to wither completely. This effect first takes place 
in the lowest leaves, and in each commences at the apex of the leaf and 
gradually extends to the point of insertion. When the leaves are com- 
pletely withered, if they are gathered and submitted separately to the 
tests that have been described, nothing can be found but some insensible 
or nearly insensible traces of the saccharine principles and of the precipi- 
table substance with which they previously abounded. Whence it appears 
that at the period of which we are treating these carbonated principles 
pass into the stem and serve it as an aliment, in the same manner as the 
analogous principles, elaborated by the leaves of exogenous trees, de- 
scend beneath the living cortical layer into the first external layers of 
the alburnum, in order to nourish the young cylinder of wood and 
bark, which like a hollow stem is annually formed and moulded upon 
the ancient skeleton of wood. 
In rye and wheat the basis of the stems therefore derive nourishment 
partly from the leaves which are attached to them and partly from the 
soil. The summit of the stem may also be supplied with aliment by its 
own leaves, and may raise the inferior sap ; but the ear, when it has left 
the stem, and especially when it has been fecundated, appears to exercise 
a powerful faculty of absorption upon the juices contained in the sum- 
mit, which must remove them rapidly, in proportion as they are fur- 
nished by the base of the stem. To satisfy myself that this was the 
fact I divided the stems of wheat, from which the leaves had been re- 
moved on the 4th of June, into two parts, the ear being in full flower, 
Of the two extracts thus formed, that of the bases contained nearly 
twice the quantity of sugar contained in the extract of the summits, 
the densities being equal. At this period also of full efflorescence the 
saccharine principles are abundant in the ears of wheat. They ex- 
ist in them in the state of sugar of starch and cane sugar, adjoined to a 
substance precipitable by alcohol, which is perfectly soluble in water, 
and has a rotation to the right like dextrine, but having less rotating 
energy and susceptible of modification by fermentation. The presence 
of cane sugar in the ears is ascertained by the rotation of the extract, 
which though strongly directed towards the right before fermentation, 
is suddenly thrown towards the left, and becomes very feeble as soon 
as that phenomenon is completed. There was nothing to indicate 
the existence of this sugar in the ears of rye before flowering, nor 
in the young grains of rye, though the stems also contained cane sugar. 
Could it arise from a difference of quality proper to the two plants ? 
Whatever it might be they each present this remarkable result, that 
_ the grape sugar of the stems does not pass in that state to the ears. 
As has been remarked above, in proportion as the fecundated ear is 
enlarged the lower leaves become yellow and withered by transmitting 
their carbonated products to the stem. The base of the stem also 
