CLUE TO THE HOMOLOGIES OF FRUITS 251 



by the balance, since it is slight in amount. The colour-change 

 again is largely due to the change in colour of the embryo. 



The last stage is occupied with the active drying of the darken- 

 ing pod, the yellow seeds contracting and hardening rapidly and 

 adopting the permanent chocolate-brown colour of the normal 

 resting seed. In this stage, however, the change in seed-colour 

 is mainly an affair of the coverings, whilst in the two earlier stages, 

 marked by green and yellow seeds, it was largely concerned 

 with the embryo. This last stage closes with the completion 

 of the drying of the pod in the sun's rays, and the pod dehisces 

 suddenly, giving rise to those curious little clicks that one hears 

 so frequently when standing near a gorse bush on a sunny day. 



Now all these changes in the seeds of Ulex europaus^ from 

 the soft green state to the hard chocolate-brown condition, 

 are carried on in the closed pod. In fact, all three stages 

 may be observed together in the same pod. The discolora- 

 tion begins at its distal end, and before the blackening process 

 has extended down one-third of the pod's length all the seeds 

 will have changed their hue from green to yellow. When 

 it has affected four-fifths of the pod, the uppermost seeds 

 will be found actively shrinking, hardening, and colouring 

 chocolate brown ; and by the time the whole pod has blackened 

 all the seeds will be in that condition. But although the 

 pod has dried considerably during the blackening process, it 

 is still fairly moist at its completion ; and the seeds, though 

 considerably reduced in size and no longer soft, are far from 

 being as hard as in the normal resting seed, and have yet to 

 decrease in size. Up to this point there has been no opening 

 of the pod, and the completion of the drying process and the 

 ultimate dehiscence are soon affected by exposure to the sun. 



It has been noted above that the green and yellow seeds 

 have green and yellow embryos, the colouring of the soft 

 seeds depending in these two stages mainly on the colour 

 of the embryos. This change from green to yellow is 

 probably connected with the failing of the nutrient supplies, 

 since it coincides with the commencement of the withering 



