Pot 3 : 6 : 16 : 3 : 4. Pot 3 : 6 2/8 : : 0 4/8.
Pot 4 : 7 3/8 : 14 : 2 5/8 : 5. Pot 4 : 6 1/8 : : 2 4/8.
Total : 56.26 : 62 : 25.75 : 15.
The average height of the eight tallest flower-stems on the crossed plants is here 7.03 inches, and that of the eight tallest flower-stems on the self-fertilised plants 3.21 inches; or as 100 to 46. We see, also, that the crossed plants bore sixty-two flower-stems; that is, above four times as many as those (namely fifteen) borne by the self-fertilised plants. The flowers were left exposed to the visits of insects, and as many plants of both forms grew close by, they must have been legitimately and naturally fertilised. Under these circumstances the crossed plants produced 324 capsules, whilst the self-fertilised produced only 16; and these were all produced by a single plant in Pot 2, which was much finer than any other self-fertilised plant. Judging by the number of capsules produced, the fertility of an equal number of crossed and self-fertilised plants was as 100 to 5.
In the succeeding year (1871) I did not count all the flower-stems on these plants, but only those which produced capsules containing good seeds. The season was unfavourable, and the crossed plants produced only forty such flower-stems, bearing 168 good capsules, whilst the self-fertilised plants produced only two such flower-stems, bearing only 6 capsules, half of which were very poor ones. So that the fertility of the two lots, judging by the number of capsules, was as 100 to 3.5.
In considering the great difference in height and the wonderful difference in fertility between the two sets of plants, we should bear in mind that this is the result of two distinct agencies. The self-fertilised plants were the product of illegitimate fertilisation during five successive generations, in all of which, excepting the last, the plants had been fertilised with pollen taken from a distinct individual belonging to the same form, but which was more or less closely related. The plants had also been subjected in each generation to closely similar conditions. This treatment alone, as I know from other observations, would have greatly reduced the size and fertility of the offspring. On the other hand, the crossed plants were the offspring of long-styled plants of the fourth illegitimate generation legitimately crossed with pollen from a short-styled plant, which, as well as its progenitors, had been exposed to very different conditions; and this latter circumstance alone would have given great vigour to the offspring, as we may infer from the several analogous cases already given. How much proportional weight ought to be attributed to these two agencies,--the one tending to injure the self-fertilised offspring, and the other to benefit the crossed offspring,--cannot be determined. But we shall immediately see that the greater part of the benefit, as far as increased fertility is concerned, must be attributed to the cross having been made with a fresh stock.
Primula veris.
EQUAL-STYLED AND RED-FLOWERED VAR.
I have described in my paper 'On the Illegitimate Unions of Dimorphic and Trimorphic Plants' this remarkable variety, which was sent to me from Edinburgh by Mr. J. Scott. It possessed a pistil proper to the long-styled form, and stamens proper to the short-styled form; so that it had lost the heterostyled or dimorphic character common to most of the species of the genus, and may be compared with an hermaphrodite form of a bisexual animal. Consequently the pollen and stigma of the same flower are adapted for complete mutual fertilisation, instead of its being necessary that pollen should be brought from one form to another, as in the common cowslip. From the stigma and anthers standing nearly on the same level, the flowers are perfectly self-fertile when insects are excluded. Owing to the fortunate existence of this variety, it is possible to fertilise its flowers in a legitimate manner with their own pollen, and to cross other flowers in a legitimate manner with pollen from another variety or fresh stock.