io6 STUDIES IN SEEDS AND FRUITS 



not uncommon to find seeds in this condition on the plant, 

 when from some cause the pod has opened prematurely or 

 has been injured in the green closed state. It would seem 

 from my experiments that, excepting complete submergence in 

 water, there are no conditions so moist as to prevent the initial 

 shrinking of the soft, full-sized so-called unripe seeds found 

 in the green pods of Guilandina bonducella. Two of these 

 seeds placed in water under cover in Jamaica floated heavily, 

 showing only a small portion protruding slightly above the 

 water. Although during three days' immersion they increased 

 their combined weight from 244 to 253 grains, they both 

 developed fine concentric fissures in the small portions of their 

 surfaces that were exposed to the air. On the following day, 

 having reached a weight of 262 grains, they sank. Here 

 immersion in water had completely checked the shrinking 

 process, except in the unsubmerged surfaces exposed to 

 the air. 



One could scarcely imagine a method less likely to produce 

 impermeability than that followed by the pre-resting or unripe 

 seeds of Guilandina bonducella. As shown by Miss White in 

 the appendix to Professor Ewart's paper, and as also brought 

 out in my own experiments, the seat of impermeability lies 

 principally in the hard prismatic layer of palisade cells beneath 

 the structureless cuticle. Yet the cracks formed normally in 

 the shrinking process are subcuticular, and as the seed contracts 

 their sides become tightly pressed together, and a layer of 

 cuticular enamel ultimately covers all. 



It may be here remarked that, as in many leguminous 

 plants, the shrinking of the seed is carried out in its entirety 

 before the dehiscence of the pod. After the pod has opened, 

 the seeds in it lie fully exposed to the sun's rays and become 

 very warm, since the parent plant thrives best on beaches 

 removed from the shade of trees. On one occasion in Jamaica 

 I roughly estimated the temperature of the seeds as they lay 

 in the gaping pod at 150° F. Although this exposure may 

 add somewhat to the seed's durability by hardening the cover- 



