Pot 5 : 18 1/8 : 16 4/8. Pot 5 : 14 7/8 : 16 2/8. Pot 5 : 16 2/8 : 14 2/8. Pot 5 : 15 5/8 : 14 2/8. Pot 5 : 12 4/8 : 16 1/8.

Pot 6 : 18 6/8 : 16 1/8. Pot 6 : 18 6/8 : 15. Pot 6 : 17 3/8 : 15 2/8.

Pot 7 : 18 : 16 3/8. Pot 7 : 16 4/8 : 14 4/8. Pot 7 : 18 2/8 : 13 5/8.

Pot 8 : 20 6/8 : 15 6/8. Pot 8 : 17 7/8 : 16 3/8. Pot 8 : 13 5/8 : 20 2/8. Pot 8 : 19 2/8 : 15 6/8.

Total : 520.38 : 449.88.

The average height of the thirty crossed plants is here 17.34, and that of the twenty-nine self-fertilised plants (one having died) 15.51, or as 100 to 89. I am surprised that the difference did not prove somewhat greater, considering that in the last experiment it was as 100 to 86; but this latter ratio, as before explained, was probably too great. It should, however, be observed that in the last experiment (Table 4/31), the crossed plants competed with plants of the third self-fertilised generation; whilst in the present case, plants derived from a cross with a fresh stock competed with self-fertilised plants of the first generation.

The crossed plants in the present case, as in the last, were more fertile than the self-fertilised, both lots being left uncovered in the greenhouse. The thirty crossed plants produced 103 seed-bearing flowers-heads, as well as some heads which yielded no seeds; whereas the twenty-nine self-fertilised plants produced only 81 seed-bearing heads; therefore thirty such plants would have produced 83.7 heads. We thus get the ratio of 100 to 81, for the number of seed-bearing flower-heads produced by the crossed and self-fertilised plants. Moreover, a number of seed-bearing heads from the crossed plants, compared with the same number from the self-fertilised, yielded seeds by weight, in the ratio of 100 to 92. Combining these two elements, namely, the number of seed-bearing heads and the weight of seeds in each head, the productiveness of the crossed to the self-fertilised plants was as 100 to 75.

The crossed and self-fertilised seeds, which remained after the above pairs had been planted, (some in a state of germination and some not so), were sown early in the year out of doors in two rows. Many of the self-fertilised seedlings suffered greatly, and a much larger number of them perished than of the crossed. In the autumn the surviving self-fertilised plants were plainly less well-grown than the crossed plants.

7. PAPAVERACEAE.--Papaver vagum.

A SUB-SPECIES OF Papaver dubium, FROM THE SOUTH OF FRANCE.

The poppy does not secrete nectar, but the flowers are highly conspicuous and are visited by many pollen-collecting bees, flies and beetles. The anthers shed their pollen very early, and in the case of Papaver rhoeas, it falls on the circumference of the radiating stigmas, so that this species must often be self-fertilised; but with Papaver dubium the same result does not follow (according to H. Muller 'Die Befruchtung' page 128), owing to the shortness of the stamens, unless the flower happens to stand inclined. The present species, therefore, does not seem so well fitted for self-fertilisation as most of the others. Nevertheless Papaver vagum produced plenty of capsules in my garden when insects were excluded, but only late in the season. I may here add that Papaver somniferum produces an abundance of spontaneously self-fertilised capsules, as Professor H. Hoffmann likewise found to be the case. (4/2. 'Zur Speciesfrage' 1875 page 53.) Some species of Papaver cross freely when growing in the same garden, as I have known to be the case with Papaver bracteatum and orientale.

Plants of Papaver vagum were raised from seeds sent me from Antibes through the kindness of Dr. Bornet. Some little time after the flowers had expanded, several were fertilised with their own pollen, and others (not castrated) with pollen from a distinct individual; but I have reason to believe, from observations subsequently made, that these flowers had been already fertilised by their own pollen, as this process seems to take place soon after their expansion.

The Effects of Cross and Self-Fertilisation in the Vegetable Kingdom Page 54

19th Century English Literature

Charles Darwin

Free Books in the public domain from the Classic Literature Library ©

Charles Darwin

All Pages of This Book