337 
Extracts from British and Foreign Journals. 
CHEMISTRY IN ITS APPLICATION TO AGRICULTURE AND 
PHYSIOLOGY. 
By A. S. Copeman, Utica, N. Y. 
CContinued t from page 289.) 
The leaves of plants first prepare or form gum sugar, or 
starch, out of the crude sap introduced by the roots; these 
matters undergo various modifications according to the con¬ 
stitution of different plants, and become subservient to their 
nourishment and development. Thus the crude sap is merely 
instrumental in supplying the leaves with the materials 
necessary for the formation of “ organic” matter; it is the 
proper juice (as the botanist calls it) manufactured by the 
leaves that forms the real nutritious fluid of the plant. The 
importance of the leaves of plants is sufficiently evident; not 
one of them can be abstracted or injured without the plant 
being deprived of a certain amount of power for generating its 
“ proper juice.” A man might as well expect to live with¬ 
out lungs, or a fish without gills, as a plant without leaves. 
In endeavouring to explain the function of respiration, in 
plants, I shall be obliged to draw rather more deeply upon 
your faith than in these experiments. The function may be 
thus expressed, that leaves decompose carbonic acid under 
the stimulus of light, fix the carbon of this substance, and 
discharge the oxygen into the atmosphere. 
Let us try a little experiment. 
Fill two or three glasses with water. Place a leaf or two 
under the water, in each, with a split shot or a small piece of 
lead on each edge, which will cause it to sink in the water 
and yet retain a vertical position. Place one in the shade and 
the other in the direct rays of the sun ; in the former you will 
observe no effect produced, in the latter numerous little 
bubbles of air (oxygen) will make their appearance under the 
surface of the leaves. 
The bubbles of air observed under ice in winter in pools 
and ditches, the bottoms of which are covered with growino- 
plants, consist of pure oxygen given off* by the leaves of the 
plants under the water. 
