392 STUDIES IN SEEDS AND FRUITS 



turn brown, the seeds respond ; and as they shrink become 

 much paler, almost white, except in the centre, which becomes 

 darker. The embryo is also paler. When the pod has 

 become dry and the seeds have acquired their normal resting 

 characters, the signs of active life are gone. The entire 

 embryo has now a yellowish hue, and the plumular bud, 

 that was beginning to expand before the influences resulting 

 in the suspension of the life of the embryo prevailed, has 

 now closed up again, its tiny leaves being closely appressed. 

 But the impress of the rest-period remains after the seed has 

 begun to germinate. The signs of wakening vitality in the 

 embryo in the early stage of germination are only displayed 

 in the lengthening of the axis or stem by the growth of the 

 radicle. The cotyledons maintain their yellowish, lifeless hue ; 

 whilst the plumule bleaches and becomes quite colourless, 

 making little or no effort to unfold its leaves again, until 

 the protruding radicle exceeds three-fifths of an inch in length. 

 The bleaching of the green plumule of the pre-resting seed 

 as the resting stage is reached probably occurs also with 

 cucurbitaceous plants. It seems to happen with the Walnut 

 (Juglans). Lord Avebury speaks of the plumule bearing five 

 or six rudimentary leaves "often just tipped with green" 

 (^Contribution to our Knowledge of Seedlings, i. 8). 



The lethargy displayed in the waking up of the dormant 

 embryo of Poinciana regia came quite as a revelation to me. 

 For some time after the radicle has struck into the soil the 

 plantlet's existence is mainly hypocotylar and scarcely cotyle- 

 donary or plumular. The plumular bud is very slow to 

 unfold its tiny leaves, so long closed up during the rest- 

 period ; but gradually it assumes a pale greenish -yellow 

 colour. So also the cotyledons retain their yellowish, lifeless 

 hue during all the germinating process. But notwithstanding, 

 they considerably increase in size by absorbing the albumen ; 

 and by the time they have extricated themselves from the 

 seed-case there is but little of the reserve food left. They 

 soon then acquire a more active green, and the plumule 



