THE SHRINKING AND SWELLING SEED 221 



limits of a species, it is shown that the relative weight is sufficiently 

 stable, although it may vary considerably within a genus (p. 192). 



(6) With reference to the influence of appendages, such as hairs 

 and wings, on the proportional weight of the coverings of a resting 

 seed, that of hairs is first dealt with. Although ordinary pubescence 

 adds but little to the weight of a seed, a copious covering of long hairs 

 may increase it by 10 per cent. ; whilst in the case of the great hair- 

 development occasionally found with seeds, as in certain Asclepiads and 

 in some malvaceous genera {Gossypium\ the weight of the hairs may 

 amount to one-fourth or even to nearly a half of the entire weight 



(P- 193)- 



(7) Coming to the influence of wings on the weight of the resting 

 seed, it is shown in the case of Swietenia, Moringa^ and Tecoma that 

 the wing or wings may make up between 4 and 14 per cent, of the 

 total weight. With ordinary " margined " seeds there would be but 

 little addition to the seed's weight (p. 195). 



(8) Discussing the function of wings in the resting seed, the author 

 points out that they serve only an accidental purpose in aiding dispersal, 

 and that they have no biological significance except in the actively 

 functioning soft seed of the living fruit. Withered leaves and dry 

 resting seeds stand in this respect in the same category. The possession 

 of wings, he shows, does not always materially assist dispersal. In the 

 case of Pine seeds and the light seeds of Tecoma stans^ wind may carry 

 them a long distance ; but Mahogany seeds are usually only carried 

 a short way ; whilst the seeds of Moringa pterygosperma are not much 

 assisted in this respect (p. 196). 



(9) With regard to wings in resting seeds, the author adopts the 

 standpoint taken by Dr Goebel respecting the parachute-apparatus of 

 dry fruits, namely, that although at times serviceable for their dispersal, 

 they were not originally developed for this end, but performed quite 

 a different function in the moist pre-resting seed. As regards winged 

 Mahogany seeds, the author contrasts the heavy, moist, flabby seeds 

 of the living, closed capsule with the dry, crisp seeds — only one-fourth 

 of their moist weight — of the dehiscing dead or dying fruit ; and he 

 regards the function of the wing in a seed in the first-named condition 

 as mainly concerned with the absorption and storage of water, the 

 absorbing surface being increased threefold and the quantity of water 

 for the seed's wants greatly augmented (p. 197). 



(10) The proportional weight of the coverings in the two other 

 conditions of the seed is then considered, and it is pointed out that, 

 knowing the relative weight of parts (coats and kernel) in all the three 

 conditions of the seed (pre-resting, resting, and swollen for germination), 

 we possess the requisite data for determining the regime of the shrinking 

 and swelling seed (p. 198). 



