2l8 



PHYSIOLOGY OF NUTRITION 



tory process was obtained from five measured values, as follows: the total 

 weight of the apparatus at the beginning (A) and at the end (B) of the experi- 

 ment, the dry weight of the seeds before (m) and after germination (n) and the 

 amount of water actually given off (O). The water eliminated during the 

 experiment, was collected in calcium chloride tubes. Supposing that the 

 weight of the empty apparatus (S) and the air therein contained (U) suffered 

 no change during the experiment, the amount of water formed by respiration 

 can be easily calculated from these data. At the beginning of the experiment 

 the amount of water contained in the seeds and in the whole system is equal 

 to A — S — U — m, which may be designated as X. At the end of the experi- 

 ment the amount of water in the system, aside from the absorption tubes, is 

 equal to В — S — U — n, which may be called Y. The amount of water re- 

 tained in the absorption tubes (0) is to be added to F, to give the 

 total amount present at the end of the experiment. The difference 

 between the amount present at the beginning and that at the end, 

 is of course the amount produced by respiration. If this difference 

 is represented by Z, then we have: 



Z=Y + 0-X = B-n + 0-A+m. 

 The results obtained by Liaskovskii may be summarized as follows: 

 i. In the early stages of germination very little water, or none 

 at all, is produced. 



2. With higher temperatures the production of water is rela- 

 tively less than with lower temperatures. 



3. There is no constant relation between the amount of carbon 

 dioxide and that of hydrogen given off. 



The low rate of water formation in the early stages of germina- 

 tion may be due to the fact that various hydrolytic processes are 

 very active at this time. How great may be the amount of water 

 fixed by hydrolytic changes will be brought out by the experiments 

 of Bonnier, to be described in the next following section. 

 §7. Liberation of Heat During Respiration. — The internal temperature of 

 the plant body is generally about the same as that of the surrounding air, and it 

 is only by very careful experimentation that it is possible to demonstrate slight 

 differences. The temperature of growing shoots usually exceeds that of the 

 surrounding air by not over о.з°С. Only two periods in the life of the plant 

 exhibit an appreciable production of heat, that of seed germination and that 

 of flowering/ The temperature of germinating seeds is from 7 to 2o°C. higher 

 than that of the surrounding air, and the difference is still more pronounced in 

 the case of opening flower buds. 1 A temperature of 49 has been observed 

 in the flowering spadix of some of the Aroideae, when that of the surrounding 

 air was only 19 . The rise of temperature is here concomitant with an 

 accelerated rate of oxygen absorption. 



1 Kraus, Gregor, Physiologisches aus den Tropen. ///. Über Blüthenwärme bei Cycadeen, Palmen 

 und Araceen. Ann. Jard. Bot. Buitenzorg 13: 217-275. 1896. 



* Large leaf buds of deciduous trees, as they open in the spring, should also be mentioned 

 here. Expanding buds of the horse-chestnut (^sculus) furnish an example. — Ed. 



Fig. 93.— 

 Calorimeter. 

 {After Reg- 

 nault.) 



