396 



STUDIES IN SEEDS AND FRUITS 



The con- 

 ditions in 

 which the 

 red colour is 

 produced and 

 the changes 

 caused 

 (dnrinp; 

 germination. 



Canavalia 

 gladiata. 



book on the Solomon Islands (p. 293) allusion is made to my 

 finding cracked seeds of Adenanthera pavonina in the gizzard 

 of a Nicobar pigeon, and it is evident that they also serve as 

 food for Indian parrots (Mr J. Scott in More Letters of Charles 

 Darwin, ii. 349). Then, again, the Layards observed in New 

 Caledonia that a small crow and diiFerent species of parrots 

 fed on the seeds of Erythrina {Ibis, vi. 1882). But this is aU 

 that I know of the matter. Mr P. H. Gosse in his book on 

 The Birds of Jamaica names a number of seeds that are eaten 

 by them, but no mention is made of any of the hard red seeds 

 above noticed. 



I will here confine my attention to the conditions under 

 which such seeds acquire their red colour and to the changes 

 they experience in this respect when absorbing water for 

 germination, as illustrated by those of Abrus precatorius, Aden" 

 anthera pavonina, and Canavalia gladiata. All three have these 

 features in common. They go through the shrinking and 

 colouring processes in the closed pod ; in all of them the soft 

 unripe seed is rose-pink in hue, the change from pink to red 

 representing the last stage in the coloration ; and, lastly, the 

 colouring matter is readily dissolved out in water, when the 

 coats are pierced or the cuticle is not intact. 



In the case of Canavalia gladiata the soft, unripe, rose-pink 

 seed belongs to the green pod. As the pod dries, the shrink- 

 ing and hardening seed assumes a bright red hue, and by th&- 

 time the pod is well dried and on the point of dehiscence the 

 seed is fully contracted and dull red. Whilst drying, the pod 

 does not discolour or darken, as seems to be the rule with 

 legumes having dark-coloured seeds ; but it becomes gradually 

 paler, and finally has a light brown, parchment-like appearance. 

 When absorbing water and swelling for germination, the seed 

 first resumes its original pink hue and then becomes a chestnut- 

 brown. As shown below under Abrus precatorius, where the 

 same thing occurs, this return of the germinating seed to the 

 colour of immaturity is really due to the hydration of the 

 coverings, the colouring matter being to some extent washed 



