EEV, G. HElSrSLOW FEETILISATIOJf OF PLANTS. 209 



found the pollen grains always penetrating the stigma. Many 

 of them fertilise themselves in the bud without opening at all. 

 The common chickweed and the Spergula arvensis in the winter 

 never open ; but the anthers will be found clustering round the 

 stigmas, and the flower seeding itself rapidly in that state. They 

 fertilise themselves with great ease and great rapidity. It is as- 

 tonishing how soon the seeds ripen and escape. 9. "Cleistogamous" 

 flowers. Certain plants, besides bearing conspicuous flowers, as 

 the common violet, have inconspicuous, almost microscopic 

 flowers as well, which never open. Kow the ordinary violet- 

 blossoms rarely set any seed ; but if you turn up the leaves in 

 the summer, you will find a great number of minute buds, not 

 much bigger than a large pin's head, but they often have no petals, 

 and the stamens are reduced to two or three, and the anthers are 

 pressed down on the stigma, and the result is that these minute 

 flowers are self-fertilising and set seed in profusion. Oxalis, or 

 the wood sorrel, is another instance ; as is one of the balsams ; and 

 Lamium amplexicaide also has cleistogamous flowers. 10. The 

 relative fertility may equal or surpass that of crossed plants. Yery 

 often the number of seeds per capsule did not difi'er much between 

 the intercrossed and the self-fertilised in Mr. Darwin's experi- 

 ments ; but the intercrossed being more vigorous produced more 

 flowers, so that the absolute fertility was very greatly in favour of 

 the intercrossed, but the number of seeds per capsule did not 

 materially differ. Then, again, the fertility does not decrease. 

 If there were injurious effects in self- fertilisation, one would think 

 that the fertility would decrease in successive generations, but it 

 does not ; and in some cases plants usually requiring to be inter- 

 crossed became veiy self -fertile, by the anthers maturing with the 

 stigma instead of before them, and Mr. Darwin found the fertility 

 then increased in successive generations. This was the case with 

 the clove pink. 1 1 . When the plants were grown in competition 

 on opposite sides of the pot, so long as they were seedlings, there 

 was no difference ; but as soon as they began to increase in size, 

 competition set in. It was with that object he put them in the 

 same pot, to resemble the "struggle" which occurs in nature. 

 But it is generally plants of different orders that compete together 

 in nature, and not plants of the same kind ; and two plants 

 of totally different orders will grow together where plants of the 

 same kind will not, for they do not require exactly the same 

 food; but two of the same kind want the same things, and so 

 compete for the same elements. Therefore it is not quite the same 

 condition as happens in nature. When, however, the seedlings were 

 planted in the open ground, there was often very little differ- 

 ence between them, and when transferred from the pots to the 

 open ground, although still in favour of the intercrossed, it was 

 much less so. There are only two alternatives to explain this ; 

 either the intercrossed lost vigour from being moved, or else the self- 

 fertilised gained vigour faster than the intercrossed, and so became 

 nearly equal to them. In Mr. Darwin's book on the " Variation of 



