A PLANT STARTING IN LIFE.
According to Chevandier, an acre of beech forest annually absorbs three and one half tons of carbonic acid gas, and from this eliminates about one ton of carbon.
Most of the oxygen and hydrogen of plants is probably obtained from the water absorbed by leaves and roots. Recent experiments indicate that plants may sometimes absorb oxygen directly from the air. This is especially true in the case of buds, as may be shown by the following experiment:
Cut twigs of willow, oak or apple just before the buds are to unfold, and place the ends in a little holder containing a small amount of water, and set this in a saucer; partially fill the saucer with quicksilver; over the twigs invert a glass fruit jar filled with oxygen, so that its mouth will be sealed by the quicksilver. The buds will unfold, and some of the oxygen disappear, but if the jar be filled with hydrogen or nitrogen the buds will decay. De Saussure,[1] by a somewhat similar experiment, proved that oxygen is absorbed by the roots of plants.
SECTION OF AN EXOGENOUS STEM.
Both gases and moisture are taken up and distributed through the cells by osmose.[2] This may easily be shown; cut off the end of a carrot and scoop out the central portion of the remainder, and place in the cavity dry sugar; this will soon be converted into a syrup, and the sides of the carrot will have perceptibly shrunk, from the passage of moisture out of the cells to the sugar.
The mineral constituents of plants are all taken up by the roots in the form of solution, water being the great carrier by which plants are supplied.
The following substances are invariably present in all agricultural plants, and in many others, viz.: Potash, soda, lime, magnesia, oxide of iron, chlorine, sulphuric acid, phosphoric acid, silicic acid, and carbonic acid. The chemical composition of different specimens of the same plant is found to be quite uniform.