HIGHLY COLOURED SEEDS 267 



not itself hard, it is often protected in some other 

 way, e.g. the seeds of the orange are very slippery 

 and bitter. We must not forget that a seed which is 

 dropped by an animal with its dung, has the further 

 advantage of a richly manured soil to germinate in, 

 and that much depends on the first stages of a plant's 

 growth. 



9. But there are some seeds which though borne 

 in dry capsule, are so brilliantly coloured as to be con- 

 spicuous from a considerable distance. For instance, 

 the small red and black or white seed of ABRUS 

 PRECATORIUS which is used by jewellers and gold- 

 smiths for weighing, the red seeds of ADENANTHERA 

 and the scarlet seeds of BIXA (fig. 53). 



The plant in this case seems to be trading on the 

 inquisitiveness and curiosity of birds. For it should 

 be noticed that, in the first two of these plants, the 

 seeds are very hard and very smooth, so hard and 

 smooth that it would require a powerful beak to break 

 them. A bird which picks such a seed, but finding it 

 too hard to crack, drops it while flying, or swallows 

 it whole and ejects it in its dung, thereby carries it 

 some distance from the tree. 



But the plant is not content with merely colouring 

 the seeds. Look at an ADENANTHERA tree when its 

 seeds are ripe. The brown pod opens, and then the 

 sides twist back so as to expose the seeds, which do 

 not fall at once as happens in most pods, but remain 

 attached by their funicles, and are all the more con- 

 spicuous because of the silvery white surface against 

 which they rest. Here we find that not only the seed 

 coat, but the inside of the pod also is coloured ta 



