106 SWELLING OF SEEDS. [CH. V 



the water will not change. This is what happens* 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. 



When seeds of certain plants are placed in water there 

 is great variability in the time which elapses before they 

 become imbibed. This is especially the case with legu- 

 minous seeds. Nobbe^ describes the phenomenon in 

 clover seeds ; we use those of a Lupin with a rough sur- 

 face to the testa. 



Take 100 Lupin seeds and place them in a flat 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 

 renewed to minimise decomposition, and this should be 

 done at intervals of 12 hours until all the seeds are 

 swollen, noting at each examination the number of freshly 

 imbibed seeds. 



The cause of the individuality in imbibition seems to 

 depend, not on the cotyledons, but on the seed coats, 

 This may be demonstrated on a similar number of seeds, 



^ Beinke shows that the increase in volume is slightly leas than the 

 water absorbed. 



' Handbuch der Samenkunde. 



