(4/3. Mr. J. Scott found 'Report on the Experimental Culture of the Opium Poppy' Calcutta 1874 page 47, in the case of Papaver somniferum, that if he cut away the stigmatic surface before the flower had expanded, no seeds were produced; but if this was done "on the second day, or even a few hours after the expansion of the flower on the first day, a partial fertilisation had already been effected, and a few good seeds were almost invariably produced." This proves at how early a period fertilisation takes place.) I raised, however, a few seedlings of both lots, and the self-fertilised rather exceeded the crossed plants in height.

Early in the following year I acted differently, and fertilised seven flowers, very soon after their expansion, with pollen from another plant, and obtained six capsules. From counting the seeds in a medium-sized one, I estimated that the average number in each was at least 120. Four out of twelve capsules, spontaneously self-fertilised at the same time, were found to contain no good seeds; and the remaining eight contained on an average 6.6 seeds per capsule. But it should be observed that later in the season the same plants produced under a net plenty of very fine spontaneously self-fertilised capsules.

The above two lots of seeds, after germinating on sand, were planted in pairs on opposite sides of five pots. The two lots of seedlings, when half an inch in height, and again when 6 inches high, were measured to the tips of their leaves, but presented no difference. When fully grown, the flower-stalks were measured to the summits of the seed capsules, with the following result:--

TABLE 4/33. Papaver vagum.

Heights of flower-stalks to the summits of the seed capsules measured in inches.

Column 1: Number (Name) of Pot.

Column 2: Crossed Plants.

Column 3: Self-fertilised Plants.

Pot 1 : 24 2/8 : 21. Pot 1 : 30 : 26 5/8. Pot 1 : 18 4/8 : 16.

Pot 2 : 14 4/8 : 15 3/8. Pot 2 : 22 : 20 1/8. Pot 2 : 19 5/8 : 14 1/8. Pot 2 : 21 5/8 : 16 4/8.

Pot 3 : 20 6/8 : 19 2/8. Pot 3 : 20 2/8 : 13 2/8. Pot 3 : 20 6/8 : 18.

Pot 4 : 25 3/8 : 23 2/8. Pot 4 : 24 2/8 : 23.

Pot 5 : 20 : 18 3/8. Pot 5 : 27 7/8 : 27. Pot 5 : 19 : 21 2/8.

Total : 328.75 : 293.13.

The fifteen crossed plants here average 21.91 inches, and the fifteen self-fertilised plants 19.54 inches in height, or as 100 to 89. These plants did not differ in fertility, as far as could be judged by the number of capsules produced, for there were seventy-five on the crossed side and seventy-four on the self-fertilised side.

Eschscholtzia californica.

This plant is remarkable from the crossed seedlings not exceeding in height or vigour the self-fertilised. On the other hand, a cross greatly increases the productiveness of the flowers on the parent-plant, and is indeed sometimes necessary in order that they should produce any seed; moreover, plants thus derived are themselves much more fertile than those raised from self-fertilised flowers; so that the whole advantage of a cross is confined to the reproductive system. It will be necessary for me to give this singular case in considerable detail.

Twelve flowers on some plants in my flower-garden were fertilised with pollen from distinct plants, and produced twelve capsules; but one of these contained no good seed. The seeds of the eleven good capsules weighed 17.4 grains. Eighteen flowers on the same plants were fertilised with their own pollen and produced twelve good capsules, which contained 13.61 grains weight of seed. Therefore an equal number of crossed and self-fertilised capsules would have yielded seed by weight as 100 to 71. (4/4. Professor Hildebrand experimented on plants in Germany on a larger scale than I did, and found them much more self-fertile. Eighteen capsules, produced by cross-fertilisation, contained on an average eighty-five seeds, whilst fourteen capsules from self-fertilised flowers contained on an average only nine seeds; that is, as 100 to 11: 'Jahrb. fur Wissen Botanik.' B.

The Effects of Cross and Self-Fertilisation in the Vegetable Kingdom Page 55

19th Century English Literature

Charles Darwin

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