Page:Popular Science Monthly Volume 16.djvu/843

Rh reveals the spores which are the analogues of seed, although they possess neither their vestments nor organs, but are simple membranous sacs (full of liquid), which germinate at some indefinite point of their convex surface into a new plant like that which produced them.

A comparison of the condition of flowering plants and of the mosses and fungi, during a phosphorescent display, will lead us to attribute the appearance to similar action of vital forces, if we for a moment review the processes by which these forces are accumulated. In the growth of plants heat acts as a dynamic agent, which the germ of the plant directs and uses. The first action of growth consists in the conversion of the starch of the seed into a soluble form, and in chemically combining the starch, sugar, oil, and albumen by fermentation into the protoplasmic matter which supplies the material for the tissues of the plant. The development of this protoplasm into organized tissue is due to the inherent power of the germ, and marks the second stage of progress. The only action of light is employed in producing higher chemical combination; heat acts as the constructive power.

The process of growth does not absorb all the elaborated materials provided, and an additional amount of heat or force is generated by the decomposition or a "retrograde transformation" of these compounds. A much greater proportion, however, of the organized substances is stored up within the structure of the plant as a "reservoir of reserved material," to meet the exhaustive process of flowering and the maturing of fruit and seed. That these processes are sustained at the expense of an extra amount of force, and by the decomposition of their own products, is evident from the unusual production of carbonic acid. The combination of carbon, oxygen, and hydrogen, in the building up of plants, is here reversed, and by a retrograde process heat is set free, which we have seen is necessary for the elaboration of reproductive agents.

This appears to be precisely the same action which takes place in the reproduction of fungoid plants and mosses. A corresponding condition is shown by the rapid exhalation of carbonic acid; indeed, Dr. Carpenter asserts that a decomposition of a portion of the absorbed material is the only conceivable source of the large quantity they are constantly giving out, and ascribes the very rapid growth of these plants to a "retrograde metamorphosis." The substances which enter into the new growth are already prepared by the foster-plant, and we find the parasite incapable of forming any new combination through the agency of light. This necessarily awakens a doubt of any action resulting from insolation or reflection in the cases of the liverworts or mushrooms which have been referred to.

The expression of light in flowering plants seems to be through the medium of electricity, while in cryptogams it resembles the steady glow of slow combustion. High microscopic power may, however, reveal, as in some cases of animal phosphorescence, the sparkle and flash