The superiority in weight of the self-fertilised seeds in at least six out of the ten cases, namely, with Brassica, Hibiscus, Tropaeolum, Nemophila, Borago, and Canna, may be accounted for in part by the self-fertilised capsules containing fewer seeds; for when a capsule contains only a few seeds, these will be apt to be better nourished, so as to be heavier, than when many are contained in the same capsule. It should, however, be observed that in some of the above cases, in which the crossed seeds were the heaviest, as with Sarothamnus and Cyclamen, the crossed capsules contained a larger number of seeds. Whatever may be the explanation of the self-fertilised seeds being often the heaviest, it is remarkable in the case of Brassica, Tropaeolum, Nemophila, and of the first generation of Ipomoea, that the seedlings raised from them were inferior in height and in other respects to the seedlings raised from the crossed seeds. This fact shows how superior in constitutional vigour the crossed seedlings must have been, for it cannot be doubted that heavy and fine seeds tend to yield the finest plants. Mr. Galton has shown that this holds good with Lathyrus odoratus; as has Mr. A.J. Wilson with the Swedish turnip, Brassica campestris ruta baga. Mr. Wilson separated the largest and smallest seeds of this latter plant, the ratio between the weights of the two lots being as 100 to 59, and he found that the seedlings "from the larger seeds took the lead and maintained their superiority to the last, both in height and thickness of stem." (9/17. 'Gardeners' Chronicle' 1867 page 107. Loiseleur-Deslongchamp 'Les Cereales' 1842 pages 208-219, was led by his observations to the extraordinary conclusion that the smaller grains of cereals produce as fine plants as the large. This conclusion is, however, contradicted by Major Hallet's great success in improving wheat by the selection of the finest grains. It is possible, however, that man, by long-continued selection, may have given to the grains of the cereals a greater amount of starch or other matter, than the seedlings can utilise for their growth. There can be little doubt, as Humboldt long ago remarked, that the grains of cereals have been rendered attractive to birds in a degree which is highly injurious to the species.) Nor can this difference in the growth of the seedling turnips be attributed to the heavier seeds having been of crossed, and the lighter of self-fertilised origin, for it is known that plants belonging to this genus are habitually intercrossed by insects.
With respect to the relative period of germination of crossed and self-fertilised seeds, a record was kept in only twenty-one cases; and the results are very perplexing. Neglecting one case in which the two lots germinated simultaneously, in ten cases or exactly one-half many of the self-fertilised seeds germinated before the crossed, and in the other half many of the crossed before the self-fertilised. In four out of these twenty cases, seeds derived from a cross with a fresh stock were compared with self-fertilised seeds from one of the later self-fertilised generations; and here again in half the cases the crossed seeds, and in the other half the self-fertilised seeds, germinated first. Yet the seedlings of Mimulus raised from such self-fertilised seeds were inferior in all respects to the crossed seedlings, and in the case of Eschscholtzia they were inferior in fertility. Unfortunately the relative weight of the two lots of seeds was ascertained in only a few instances in which their germination was observed; but with Ipomoea and I believe with some of the other species, the relative lightness of the self-fertilised seeds apparently determined their early germination, probably owing to the smaller mass being favourable to the more rapid completion of the chemical and morphological changes necessary for germination. On the other hand, Mr. Galton gave me seeds (no doubt all self-fertilised) of Lathyrus odoratus, which were divided into two lots of heavier and lighter seeds; and several of the former germinated first.