Page:The Scientific Monthly vol. 3.djvu/179

Rh terms of physics and chemistry. What was regarded 100 years ago as a special vital force in the life of plants proved to be an adaptation of physico-chemical forces. The chemical action of chlorophyll is not fully understood, but it is known to absorb most vigorously the solar rays between B and C of the spectrum, and these rays are most effective in assimilation. While the effect of the solar rays between D and E is minimal those beyond F are again effective. In heliotropic movements both of plants and animals the blue rays are more effective than the red. Spores given off as ciliated cells from the algæ seek first the blue rays. Since the food supply of animals is primarily derived from chlorophyll-bearing plants animals are less directly dependent on the solar light and solar heat while the chemical life of plants fluctuates throughout the day with the variations of light and temperature. Thus Richards finds in the escti that the breaking down of the acids through the splitting of the acid compounds is a respiratory process caused by the alternate oxidation and deoxidation of the tissues through the action of the sun.

��^<3, 2. Thbeb Bbdions or thb Solas Sfecthdm skowinq tub Lines or ^ttos, Nitrogen, Calcidu, Ibok, Maonbsieii, Sodidu anu HtcHoaEN. From tba »' Mt, Wllion OtaeiTBWCj.

The solar energy transformed into the chemical potential energy of the compounds of carbon, hydrogen, and oxvfren in the plants is trans- mntd by the animal into motion and heat and then dissipated. Thus in the life cycle we observe both the conservation and the degradation of

MLoeb, Jacquea, 1906, p. 115.

"Op. «(., p. 127.

t» Hieharda, Herbert M., 1915, pp. 34, 73-75.

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