SEED-COLORATION 



377 



ment of the black mottling of the seeds that the pods should 

 be left undisturbed on the plant. No mottling took place in 

 any of my experiments on detached green pods with soft green 

 seeds, whether the pod was allowed to dry in air or was placed 

 in wet conditions, as in water or in wet moss. Experimenting 

 on the soft green pre-resting seeds, 1 found that when totally 

 submerged in water they failed to mottle and that when 

 allowed to dry in air they did so very imperfectly. But when 

 a soft green seed was placed on the surface of water so that a 

 portion was exposed, in the course of a few days the exposed 

 portion displayed mottling, whilst the under submerged part 

 remained green. These results seem to signify that mottling 

 occurs under conditions intermediate between those to which 

 the air-drying seed and the submerged seed are subjected, 

 such as would be presented in the confined conditions of the 

 closed green pod. 



These indications of the Vicia seeds will become more 

 significant when we come to consider those of other 

 leguminous seeds. It is more difficult than usual in their 

 case to dissociate the coloration of the seeds from the drying 

 of the pod ; but the data go to show that the seeds of Vicia are 

 capable of hardening and of acquiring their dark coloration in 

 the moist green pod. In this case the drying of the pod 

 might be regarded as interfering with the completion of the 

 blackening process ; and in this way the dark mottling would 

 present itself as the result of a check in the progressive blacken- 

 ing of the seed. We would thus take it that Vicia seeds are 

 mottled because they have failed to become uniformly black. 



More determinate results are offered in the blackening of 

 the large, soft, white pre-resting seeds of two other leguminous 

 plants, Mucuna urens and Dioclea reflexa ; and I will let each 

 tell its own story. 



With Mucuna urens, where the immature seeds in the 

 green pod are white, the soft unripe seeds harden and blacken 

 as the pod dries and browns, completing all their changes in 

 the closed pod, though the dark hue usually becomes paler 



The blacken- 

 ing of the 

 seeds of 

 Mucuna 

 urens. 



