378 



STUDIES IN SEEDS AND FRUITS 



and of a blackish grey when the seeds assume the final resting 

 state. The changes in the seed are preceded by the shrinking 

 of the fleshy cord or funicle and by the blackening of the 

 raphe and scar, the rest of the seed's surface remaining for a 

 time a pure white. These seeds do not mottle ; but it is 

 significant that though there is every appearance of a connection 

 between the drying of the pod and the blackening of the seeds, 

 the soft white seeds when detached blacken much more rapidly 

 when wetted than when allowed to dry. Here, it seems, 

 drying retards the process. It may be added that the 

 subsequent blackening of the shrinking seed is apparently not 

 connected with the previous blackening of the raphe and scar 

 when the cord withers. The same thing happens with some 

 white seeds (like those of Canavalia ensiformis) when the cord 

 dries up, the black scar remaining a permanent feature of the 

 white matured seed. 



From these indications of the seeds of Mucuna urens we 

 turn to those supplied by the seeds of the kindred plant, 

 Dioclea reflexa. These seeds are also white when immature in 

 the green pod, and when the pod darkens, as it begins to dry 

 up, the seeds commence to shrink, harden, and blacken. But 

 there is this difference. The blackening process is usually 

 incomplete, and mottled seeds result. They also follow the 

 general rule that the seed acquires its fixed characters as a 

 resting seed, whether in colour or in other respects, in the 

 closed pod. As in Vicia sadva and Vicia septum^ three kinds 

 of seeds as regards their colour can be distinguished, the black 

 or brownish black, the reddish brown, and the mottled seed 

 showing black patches on a reddish-brown ground. As in 

 Vicia also, the mottled seeds are most typical of the plant, and 

 the mottling may be regarded as the failure of the blackening 

 process. But in Vicia the black seed represents the end of the 

 colouring process, whilst in Dioclea it represents the beginning. 

 When the blackening of a Dioclea seed fails altogether the 

 seed is reddish brown ; but when the process is only partly 

 checked there are formed black patches on a reddish-brown 



