The naturally crossed seedlings derived from the crossed plants flowered in all three pots before the naturally crossed seedlings derived from the self-fertilised plants. When both lots were in full flower, the two tallest plants on each side of each pot were measured, and the result is shown in Table 4/42.

TABLE 4/42. Viola tricolor: seedlings from crossed and self-fertilised plants, the parents of both sets having been left to be naturally fertilised.

Heights of plants measured in inches.

Column 1: Number (Name) of Pot.

Column 2: Naturally Crossed Plants from artificially crossed Plants.

Column 3: Naturally Crossed Plants from Self-fertilised Plants.

Pot 1 : 12 1/8 : 9 6/8. Pot 1 : 11 6/8 : 8 3/8.

Pot 2 : 13 2/8 : 9 6/8. Pot 2 : 10 : 11 4/8.

Pot 3 : 14 4/8 : 11 1/8. Pot 3 : 13 6/8 : 11 3/8.

Total : 75.38 : 61.88.

The average height of the six tallest plants derived from the crossed plants is 12.56 inches; and that of the six tallest plants derived from the self-fertilised plants is 10.31 inches; or as 100 to 82. We here see a considerable difference in height between the two sets, though very far from equalling that in the previous trials between the offspring from crossed and self-fertilised flowers. This difference must be attributed to the latter set of plants having inherited a weak constitution from their parents, the offspring of self-fertilised flowers; notwithstanding that the parents themselves had been freely intercrossed with other plants by the aid of insects.

10. RANUNCULACEAE.--Adonis aestivalis.

The results of my experiments on this plant are hardly worth giving, as I remark in my notes made at the time, "seedlings, from some unknown cause, all miserably unhealthy." Nor did they ever become healthy; yet I feel bound to give the present case, as it is opposed to the general results at which I have arrived. Fifteen flowers were crossed and all produced fruit, containing on an average 32.5 seeds; nineteen flowers were fertilised with their own pollen, and they likewise all yielded fruit, containing a rather larger average of 34.5 seeds; or as 100 to 106. Seedlings were raised from these seeds. In one of the pots all the self-fertilised plants died whilst quite young; in the two others, the measurements were as follows:

TABLE 4/43. Adonis aestivalis.

Heights of plants measured in inches.

Column 1: Number (Name) of Pot.

Column 2: Crossed Plants.

Column 3: Self-fertilised Plants.

Pot 1 : 14 : 13 4/8. Pot 1 : 13 4/8 : 13 4/8.

Pot 2 : 16 2/8 : 15 2/8. Pot 2 : 13 2/8 : 15.

Total : 57.00 : 57.25.

The average height of the four crossed plants is 14.25, and that of the four self-fertilised plants 14.31; or as 100 to 100.4; so that they were in fact of equal height. According to Professor H. Hoffman, this plant is proterandrous (4/7. 'Zur Speciesfrage' 1875 page 11.); nevertheless it yields plenty of seeds when protected from insects.

Delphinium consolida.

It has been said in the case of this plant, as of so many others, that the flowers are fertilised in the bud, and that distinct plants or varieties can never naturally intercross. (4/8. Decaisne 'Comptes-Rendus' July 1863 page 5.) But this is an error, as we may infer, firstly from the flowers being proterandrous,--the mature stamens bending up, one after the other, into the passage which leads to the nectary, and afterwards the mature pistils bending in the same direction; secondly, from the number of humble-bees which visit the flowers (4/9. Their structure is described by H. Muller 'Befruchtung' etc., page 122.); and thirdly, from the greater fertility of the flowers when crossed with pollen from a distinct plant than when spontaneously self-fertilised. In the year 1863 I enclosed a large branch in a net, and crossed five flowers with pollen from a distinct plant; these yielded capsules containing on an average 35.2 very fine seeds, with a maximum of forty-two in one capsule. Thirty-two other flowers on the same branch produced twenty-eight spontaneously self-fertilised capsules, containing on an average 17.2 seeds, with a maximum in one of thirty-six seeds.

Charles Darwin

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