CH. V] SWELLING OF SEEDS. 117 



graduated tube. Half fill bottle A with whole peas, and 

 place the same quantity of split peas in B. Fill both 

 bottles with water which has acquired the temperature of 

 the room, and take care to get rid, by shaking, of any air 

 adhering to the peas ; force in the corks firmly, and note 

 the height of the water column in each bottle. If the peas 

 increase in volume by the amount of the water absorbed, 

 the level of the water will not change. This is what 

 happens 1 in B, which contains the split peas, but in A the 

 level rapidly rises and then falls. This curious phenomenon 

 is said to be due to the expansion of the testas of the peas 

 producing a temporary increase in size. 



(137) Variability in the swelling of seeds. 



In the case of certain plants, there is great variability 

 in the time required for the absorption of water by the 

 seeds. This is especially the case with leguminous seeds. 

 Nobbe 2 describes the phenomenon in clover seeds ; we 

 use those of Lupinus hirsutus, which have a rough surface 

 to the testa. 



Take 100 lupin seeds and place them in a flat-bottomed 

 vessel (so that they may be easily examined) and add 

 about a liter of tap water. After 24 hours the majority 

 of the seeds will be swollen, the minority which have not 

 yet swollen can be easily distinguished by their smaller 

 size. 



The swollen seeds should be removed and the water 



1 Eeinke shows that, in some cases of imbibition, the increase in 

 volume is slightly less than the water absorbed. Hanstein's Botan. 

 Abhand. iv. 1879, p. 60. 



2 Handbuch der Samenkunde, 1876, p. 112. 



