METABOLIC PROCESSES IN THE PLANT. 277 



potash is rapidly dissolved by the water above the mercury, and 

 since the potash solution formed absorbs the Carbon dioxide de- 

 veloped by the normal respiration of the seedlings, we can at 

 any time make fresh readings to determine the amount of Carbon 

 dioxide produced. This method, it is true, does not by any 

 means afford such accurate results as that indicated in 102. 



If we allow the experiments on intramolecular respiration to 

 proceed for a considerable time, e.g. a few days, we shall find 

 that a given quantity of seedlings, in unit time and under con- 

 stant external conditions, produce less and less Carbon dioxide. 

 The seedlings gradually pass into a pathological condition, and it 

 is important to know this, because it follows that in comparative 

 researches on intramolecular and normal respiration we must not 

 take too long an experimental period (only about six to eight 

 hours). Such comparative experiments teach, further, that only 

 a few plants, e.g. seedlings of Vicia Faba, produce as much Carbon 

 dioxide in intramolecular as in normal respiration. Most plants 

 give off much larger quantities of Carbon dioxide in presence of 

 Oxygen than when Oxygen is absent. 



See Wortmann, Arbeiten d. botan. Instituts in Wtirzburg, Bd. 2. 



105. Analytical Researches on Respiration. 



In order to deal with many questions relating to respiration, 

 it is essential to determine the quantity of Carbon, Hydrogen, and 

 Oxygen in the research material at the beginning of the experi- 

 ments and at their close. If, e.g., we ascertain the absolute quantity 

 of these elements contained in 100 gr. of seeds, and in the seedlings 

 produced after a certain time from 100 gr. of seeds, we obtain com- 

 parable numbers which at once indicate the quantity of Carbon, 

 Hydrogen, etc., consumed in respiration. Such ultimate analytical 

 researches are of special significance if, e.g., we are dealing with the 

 question, whether the whole of the Carbon lost by germinating seeds 

 is given off in the form of Carbon dioxide, or whether in germina- 

 tion other carbonaceous gases are produced (Carbon monoxide, 

 Hydrocarbons). In such researches we compare the results of 

 direct Carbon dioxide determinations, which are to be made in the 

 ma uner indicated in 102> with the results of the analyses of seeds 

 and seedlings. If there is a close agreement between the numbers 

 obtained from the respiratory investigations of the loss of Carbon 



