THE THREE CONDITIONS OF THE SEED 45 



Thus, a seed of Entada scandens weighing 400 grains in the 

 resting state will be ready to germinate under normal condi- 

 tions when it has increased its weight by water-absorption to 

 from 950 to 1000 grains. But if the conditions are unfavour- 

 able and it fails to germinate, it will continue absorbing water 

 until it reaches a condition of saturation, when its weight will 

 be about 1 150 or 1 160 grains. Thus : 



In other experiments seeds often continued to absorb water 

 long after they had failed to germinate. They may occasion- 

 ally germinate when the swelling ratio has far exceeded the 

 normal limits, but only in an imperfect and belated fashion. 

 One or two more instances will serve to illustrate these points. 

 A seed of Albizzia Lebbek, 1 grains in weight, only requires to 

 increase its weight to 4*5 grains in order to germinate ; but 

 when it has failed to germinate it will continue absorbing 

 water without rupturing its coat until nearly 6 grains in weight, 

 the limits of the normal swelling ratio, 2*25, being long passed. 

 So, again, a permeable seed of Entada polystachya^ weighing 

 7 grains, germinates usually after its weight has been increased 

 by the absorption of water to about 16 grains, its swelling ratio 

 being 2-3 ; but when it fails it continues to swell and reaches 

 a weight of 21 grains and over, thus tripling its original weight 

 to no purpose. Convolvulaceous seeds, possessing in the 

 resting stage a hard, dry albumen, are especially liable to take 

 up more water than is needed for germination. In its transi- 

 tion into the mucilaginous state, the albumen absorbs a very 

 large amount of water. The normal swelling ratio for a seed of 

 Ipomcea pes-capra is about 2-5, but seeds may germinate tardily 



