200 Proceedings of the Royal Physical Society. 



when contrasting the tropical and mountain forms. High 

 nutrition in those which have a large leaf-area tends 

 evidently to the greater specialisation of the plant along the 

 line of greater asexual vegetative growth, and its tendency 

 to reproduce itself is checked. As regards the ash con- 

 stituents, high nutrition, as seen in plants under cultivation, 

 apparently also tends to the greater specialisation of vegeta- 

 tive growth, and generally leads to the plant stuffing its 

 roots, tubers, or fruits with more simple products of 

 anabolism. Darwin, in his " Variation under Domestica- 

 tion," states that sterility is produced in plants by too much 

 manure, warmth, or dampness, causing them to run to leaf, 

 and that this is seen in alpine or peat plants brought into 

 the rich soil of gardens. He also notices the tendency to 

 produce double flowers. The sterility as seen in the seedless 

 fruits of high cultivation might be mentioned here. All 

 these tendencies in cultivated plants are of course favoured 

 by artificial selection, but they must occur in the first place 

 to be selected; and it seems probable, as is generally supposed, 

 that the results are due to the high nutrition. On the other 

 hand, the check to nutrition in plants, by pruning or placing 

 in small pots, appears to retard the specialisation of ordinary 

 vegetative growth, and to hasten the production of sporo- 

 phylls. The intense fertility of alpine or peat-loving plants 

 misht be noticed in this connection, and the burst of blossom 

 in the heather and the little moss campion are familiar 

 examples. It is to be remarked that the great specialisation 

 of form and colour on the part of the petals and other parts 

 of the flower have been brought about secondarily in the 

 higher forms of plants by the increasingly great necessity for 

 cross-fertilisation, and the brightness of flowers is probably 

 to be chiefly attributed to this. In animals there appears to 

 be an optimum-minimum of nutrition tending to the greatest 

 show of energy. The senses are well known to be heightened 

 by hunger. Starving seems to hurry on metamorphosis, 

 while over-nutrition delays it, and allows of further growth; 

 and it is evident that the increasing length of time in the 

 high nutrition of embryonic life, seen in the higher verte- 

 brates, allows of the acquirement of greater size and delays 



