194 



PHYSIOLOGY OF NUTRITION. 



73. Further Experiments on the Absorption of Water by Seeds. 

 The quantity of water which has been absorbed by different 

 kinds of seeds, when fully soaked, is by no means the same. The 

 capacity for absorbing water is therefore different in different 

 kinds of seeds. We determine the weight of a few air-dry wheat- 

 grains and peas, and then put them in water for twenty-four hours. 

 At the end of this time we dry the seeds well, and again determine 

 their weight; then return them to the water and once more 

 weigh after six hours. Further weighings may need to be made, 



but at all events it will be found 

 that, when the weight of the seeds 

 has become fairly constant, the 

 peas contain more water when 

 fully soaked than the wheat- 

 grains. Peas take up about 100 

 per cent, of their weight of water, 

 wheat grains only 40 to 60 per 

 cent. 



In many cases (e.g. beans, peas) 

 investigation at once proves that 

 the volume of the seeds, when 

 they have been soaked, is much 

 greater than when they are air- 

 dry. But the question also arises 

 whether the total volume of seeds 

 and water is changed in the pro- 

 cess of soaking. The following 

 experiment may be made to answer 

 this question. We use the ap- 

 paratus drawn in Fig. 72. In a 

 flask of about 600 c.c. capacity we 

 place 300 gr. of peas (I used white 

 Griant peas), the flask is then 

 completely filled with water and 

 immediately fitted with a two- 

 holed rubber stopper. Through 

 one hole passes a thermometer, 



FiG. 72. Apparatus for observing the 

 phenomena of absorption of water. through the other a straight glass 



tube 0'5 cm. in diameter. The 

 position of the water in the latter may easily be determined at 



