398 



STUDIES IN SEEDS AND FRUITS 



The longj 

 duration of 

 the red 

 colour de- 

 pends on the 

 impermea- 

 bihty of the 

 seed. 



Red seeds do 

 not stain 

 water red. 



The red seeds of these three plants are more or less 

 impermeable to liquid water. With Adenanthera pavonina all 

 the seeds are typically impermeable, with Ahrus precatorius the 

 great majority are, and with Canavalia gladiata the minority 

 perhaps are impermeable. The impermeable seeds are of 

 necessity non-hygroscopic, whilst the permeable seeds behave 

 hygroscopically. A seed that responded in its changes of 

 weight to the varying degrees of humidity of the atmo- 

 sphere could scarcely be expected to retain its bright red 

 hue for a long period. Where the impermeable cuticle 

 remains intact the colour ought to withstand the test of 

 centuries. This would probably be true of the seeds of 

 Adenanthera pavonina. Except when kept in unusually 

 dry conditions, I should not expect the seeds of Ahrus 

 precatorius to preserve untarnished for many years their 

 original scarlet hue, since the scar is their point of weak- 

 ness. As an indication in this direction I may refer to 35 

 seeds of Ahrus precatorius^ now beside me, which I gathered 

 from the plant in Fiji twelve years ago. Only 25, or 

 71 per cent., retain their original bright colour, the rest 

 being brownish or even blackish in hue. This is a point 

 in the history of red seeds that seems to be worthy of 

 further investigation — I mean the permanence of the colour. 

 Abundant data would be at hand in our own museums and in 

 tropical countries. 



I may here refer to a curious fact that must be well known 

 to students of vegetable chemistry. Although the red seeds 

 of Ahrus precatorius^ Adenanthera pavonina^ and Canavalia 

 gladiata stain water freely when the water is allowed to 

 penetrate their coats, the solution has not the colour of the 

 seeds. The seeds of Adenanthera impart a beautiful amber hue 

 to the water, which deepens after the seeds have been removed 

 and becomes like brown sherry. On the other hand, the 

 seeds of Ahrus and Canavalia stain the water a dark green, 

 which deepens after the seeds have been taken out, becoming 

 steely or almost inky. 



