HEAT EQUIVALENT OF NUTRIENTS OF FOOD. 591 



But eveu those plauts which possess the power of transforming 

 inorganic into organic matter can do this only under two conditions. 

 A chlorophj'll apparatus is necessary, and this must be acted upon by 

 light and heat waves of definite intensity. 



While the seed is sprouting and the first organs of the young plant 

 are being formed, the organism subsists on food which was stored up 

 in the seed, and not upon carbon dioxid, water, etc. This food fur- 

 nishes not only the material from which new tissue is produced, but also 

 the energy which each organism must have from the first moment of 

 its existence. The energy furnished by the organic material of the 

 seed takes the form of heat and furnishes the considerable quantity of 

 vital force which the young plant needs in overcoming the obstacles to 

 its existence. It is no slight task for the delicate sprouting plant to 

 force away the earth which covers it and work its way to the light. 

 When this is accomplished, although the young plant be kept away 

 from the light or the amount of heat be insufficient, it will neverthe- 

 less grow, but without being benefited by the carbon dioxid, etc., even 

 if they are present in abundance. The growth and strength are all 

 derived from the material stored up in the seed, and growth continues 

 only as long as the supply lasts. 



The inorganic substances are valuable for plants possessing chlo- 

 rophyll apparatus only so long as the conditions prevail which favor 

 assimilation. When sunlight is lacking no new organic material is 

 formed. However, the plant lives, grows, and breathes as energetically, 

 and perhaps even more energetically, during the night than during the 

 day. It lives, grows, and breathes both by night and by day from 

 organic, energy-furnishing substance. We must, therefore, consider 

 that the green plants and those lacking green color agree essentially as 

 regards the condition of nutrition. 



The green plants differ from the others only in that they possess 

 organs which have the power of utilizing the energy which comes to 

 them from the sun. They can break up the carbon dioxid and change 

 it into organic compounds which serve for food and other requirements 

 of the plant, and thus a large part of the energy of the sunlight is 

 stored up in the newly formed organic compounds. 



Just as all plants live upon organic compounds which they them- 

 selves produce or obtain ready-made from some other source, so all ani- 

 mals also live upon organic substance. 



Herbivorous animals live upon the substances stored up in the jilants, 

 and carnivorous animals upon the substances which the herbivorous 

 animals, which become their prey, have obtained from plants. 



There is no more a fundamental difference between plant and animal 

 life than there is between green plants and those lacking chlorophyll. 

 The conditions essential for life in the plant and animal world are there- 

 fore alike. The plant which lacks green coloring matter x)erishes when 



