CORRELATION OF VITAL AND PHYSICAL FORCES. 161 



Hence, also, food in the organic form must be, and is, laid up from the 

 previous year in the body of the tree. A portion of this is consumed 

 with the formation of CO a and H a O, in order to create force for the 

 development of the buds. So soon as by this means the leaves are 

 formed, the plant begins to draw force from the sun, and food from 

 the mineral kingdom. 



4. Pale Plants. — Fungi and etiolated plants have no chloro- 

 phyl, therefore cannot draw their force from the sun, nor make or- 

 ganic matters from inorganic. Hence these also must feed on organic 

 matter : not, indeed, on starch, dextrine, and protoplasm, but on decay- 

 ing organic matter. In these plants the organic matter is taken up in 

 some form intermediate between the planes No. 3 and No. 2. The 

 matter thus taken up is, a portion of it, consumed with the formation 

 of CO a and HO, in order to create force necessary to organize the re- 

 mainder. To illustrate : Matter falling from some intermediate point 

 between No. 2 and No. 3 to No. 2, produces force sufficient to raise 

 matter from the same intermediate point to No. 3 ; a portion runs to 

 waste downward, and creates force to push the remainder upward. 



5. Growth of Green Plants at Night. — It is well known that 

 almost all plants grow at night as well as in the day. It is also known 

 that plants at night exhale CO a . These two facts have not, however, 

 as far as I know, been connected with one another, and with the prin- 

 ciple of conservation of force. It is usually supposed that in the night 

 the decomposition of CO a and exhalation of oxygen are checked by 

 withdrawal of sunlight, and some of the CO a in the ascending sap is 

 exhaled by a physical law. But this does not account for the growth. 

 It is evident that, in the absence of sunlight, the force required for the 

 work of tissue-building can be derived only from the decomposition 

 and combustion of organic matter. There are two views as to the 

 source of this organic matter, either or both of which may be correct : 

 First. There seems to be no doubt that most plants, especially those 

 grown in soils rich in humus, take up a portion of their food in the 

 form of semi-organic matter, or soluble humus. The combustion of a 

 portion of this in every part of the plant, by means of oxygen also ab- 

 sorbed by the roots, and the formation of CO a , undoubtedly creates a 

 supply of force night and day, independently of sunlight. The force 

 thus produced by the combustion of a portion might be used to raise 

 the remainder into starch, dextrine, etc., or might be used in tissue- 

 building. During the day, the CO a thus produced would be again 

 decomposed in the leaves by sunlight, and thus create an additional 

 supply of force. During the night, the CO a would be exhaled. 1 



Again : It is possible that more organic matter is made by sun- 

 light during the day than is used up in tissue-building. Some of this 

 excess is again consumed, and forms CO a and H a O, in order to con- 



1 For more full account, see my paper, American Journal of Science^ November, 1859, 

 sixth and seventh heads. 

 vol. iv. — 11 



