Considering the facts now adduced, including the appearance of those varieties which are more fertile and taller than their parents and than the intercrossed plants of the corresponding generation, it is difficult to avoid the suspicion that self-fertilisation is in some respects advantageous; though if this be really the case, any such advantage is as a rule quite insignificant compared with that from a cross with a distinct plant, and especially with one of a fresh stock.  Should this suspicion be hereafter verified, it would throw light, as we shall see in the next chapter, on the existence of plants bearing small and inconspicuous flowers which are rarely visited by insects, and therefore are rarely intercrossed.

Relative weight and period of germination of seeds from crossed and self-fertilised flowers.

An equal number of seeds from flowers fertilised with pollen from another plant, and from flowers fertilised with their own pollen, were weighed, but only in sixteen cases.  Their relative weights are given in the following list; that of the seeds from the crossed flowers being taken as 100.

Column 1:  Name of Plant.

Column 2:  x, in the expression, 100 to x.

Ipomoea purpurea (parent plants):  127. 
Ipomoea purpurea (third generation):  87. 
Salvia coccinea:  100. 
Brassica oleracea:  103. 
Iberis umbellata (second generation):  136. 
Delphinium consolida:  45. 
Hibiscus africanus:  105. 
Tropaeolum minus:  115. 
Lathyrus odoratus (about):  100. 
Sarothamnus scoparius:  88. 
Specularia speculum:  86. 
Nemophila insignis:  105. 
Borago officinalis:  111. 
Cyclamen persicum (about):  50. 
Fagopyrum esculentum:  82. 
Canna warscewiczi (3 generations):  102.

It is remarkable that in ten out of these sixteen cases the self-fertilised seeds were either superior or equal to the crossed in weight; nevertheless, in six out of the ten cases (namely, with Ipomoea, Salvia, Brassica, Tropaeolum, Lathyrus, and Nemophila) the plants raised from these self-fertilised seeds were very inferior in height and in other respects to those raised from the crossed seeds.  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