RESPIRATION AND FERMENTATION 141 



logical features. Upon this subject the student, following the 

 general method indicated below under photosynthesis (page 

 113), should now arrange and express his knowledge. 



Respiratory Quantities. As to the amount oj carbon dioxide released, 

 for leaves the quantities determined by Sachs, by Brown, and by Black- 

 man, in papers already cited under Photosynthesis, vary considerably, but 

 approximate, respectively, to 30-40, 60, 80 cc. per square meter of leaf per 

 hour at ordinary temperatures, of which we may take 60 cc, which is ,12 

 grams, as the mean. Hence we may derive a conventional constant of .12 

 gm 2 h for 20 . Respiration, however, rises very rapidly with temperature, 

 approximating in leaves to o at o°, rising to .12 gm 2 h for 20°, to .30 gm 2 h for 

 30°, to .65 gm 2 h for 40°. It is to be noticed that Brown claims a very much 

 higher rate of respiration for greenhouse plants. As to seeds, certain figures 

 given by Jost (193) would yield a conventional constant of 30 grams (15 

 liters) per kilogram of dry substance per hour at ordinary temperatures, 

 that is, 30 gkh, and for buds about half that amount, or 15 gkh, while the 

 corresponding amount for herbaceous leaves, which weigh about 30 g. per 

 square meter of dry substance, would be 4 gkh. This gkh system is readily 

 transformable to the glh system (page 22) by multiplying by .5 (carbon 

 dioxide weighing approximately 2 grams per liter). 



As to amount oj energy released, it is shown by Brown (Nature, 71, 

 190^, 522) that one gram of the conventional photosynthate yields on respira- 

 tion with free oxygen 3760 calories (or more, according to others, fide Peirce, 

 "Plant Physiology," 22), in round numbers 4000 calories. The combustion 

 energy of one gram of carbon (charcoal) approximates 8000 calories, whence 

 it follows that the respiration energy of the photosynthate is about half the 

 combustion energy of an equal weight of the best fuel. Brown has also 

 shown that in a leaf of sunflower the respiration energy is equal to 349.2, 

 in round numbers 350, calories per square meter per hour, which agrees 

 well with an independent result obtained by calculation from the data above. 



As to quantities of gases exchanged, this must be, conventionally at least, 

 the reciprocal of the amounts in photosynthesis, earlier considered. 



Terminology and Conceptions of Respiration. The term Respira- 

 tion was early adopted from animal physiology, where it is still used loosely 

 to signify not only the release of energy, but also the gas exchanges incidental 

 thereto, and even the mechanical and forcible intaking and expulsion of air 

 from the body, something not found at all in plants. To give greater pre- 

 cision to the central idea of the process, Barnes, in his paper cited below 

 under Literature, has proposed the term Energesis. Since the old usage 

 will not be displaced, the best we can do is to regulate its use, and we may 

 well employ the terms for the future as follows: Respiration, an essential 

 process in plants and animals whereby oxygen is brought into chemical 

 union with carbon and hydrogen, with formation of carbon dioxide and water, 

 resulting in energesis, or a release of energy utilizable immediately by the 

 organism in its work, the mechanical movements of the gases being promoted 



