ABSORPTION OF WATER BY SEEDS. 



468 



1202. The increase of seeds in size accompanying the absorp- 

 tion of water is ascertained by placing them from time to time 

 in a narrow graduated cylinder, pouring over enough water 

 to completely cover them, and noting the height at which the 

 water stands ; then pouring it into another graduated glass and 

 accurately measuring it. The difference in amount of water in 



\j ^? 



each case indicates the volume of the seeds. The work must 

 be done expeditions!}' in order to avoid the error arising from 

 absorption during the period of measuring; but this error in 

 any case is slight. 



* cu 



1203. The following results may be of interest and serve AS a 

 guide to the student. 1 



65.418 grams of air-dried peas, having a volume of 43 cubic 

 centimetres, were soaked in water at a temperature of 19- 

 21 C. The soaked seeds were at each measurement carefully 

 dried by blotting-paper : 



The gain in weight in 70 hours was therefore 96 per cent, and 

 in volume 167 per cent. 



In another experiment the changes were as follows : Phaseolus 

 vnlgaris gained in weight, in 48 hours, 100.7 per cent, and in 

 volume, 134.14 per cent. In still another experiment, with the 

 same species, the gain in weight in 72 hours was 114.5 per cent 

 (or, taking into account some loss by extraction, 117.5 per cent), 

 and in volume, 140.9 per cent. The gain in volume is con- 

 siderablj* greater than the gain in weight. 2 



1 Xobbe : Hamlbuch der Samenkunde, 1876, p. 122. 



2 It must be rioted that in many dry seeds, for instance between the coty- 

 ledons of some peas and beans, there are cavities which must be filled before 

 there can be any marked increase of volume (Xobbe : Handbuch der Samen- 

 kunde, 1876, p. 125). 



