ORIGIN OF SPECIES IN NATURE. 



267 



corroborates this fact, for he says that his own cold and wet soil 

 tends to make his double daffodils to become single. 



Mr. Darwin, some fifty-five years ago, noticed and described, 

 in the Gardeners' Chronicle (1843, p. 628), some double flowered 

 Gcntlana Amarella, " which grew on a very hard, dry, bare, 

 chalk bank." Similarly he found on an adjoining field of 

 " wretchedly sterile clay great numbers of Ranunculus repens, 

 producing half-double flowers." He then asks the question, 

 " Is it, then, too bold a theory to suppose that all double flowers 

 are first rendered, by some change in their natural condition, 

 to a certain degree sterile?" When a double-flowering plant 

 has this affection well fixed in its constitution, then it would 

 seem that it is benefited by a rich soil ; " petalody " having set 

 in, it may affect every part of the flower — stamens first, then 

 pistil or calyx, and finally the petals may be multiplied indefi- 

 nitely, so that a flower of the double stock may contain more 

 than fifty petals. 



That the petalody can be "in the blood," so to say, is seen 

 from the fact that, as no seed can be raised from a " perfectly " 

 double stock, they can be procured from the " single " flowers. 

 For by suppressing the anthers of flowers before they shed their 

 pollen, the seeds (M. Verlot observes) developed in the ovaries 

 of these flowers produce double-flowering plants with great 

 facility — viz. 60 to 70 per cent. If the anthers be not removed, 

 then the percentage drops to 20 to 80 of double-flowering off- 

 spring, the number of seed being reduced to five or six in a pod, 

 which produced double-flowering plants, instead of from forty to 

 fifty. 



As another influence, that of age may be mentioned. Thus, 

 seed of Matthiola annua, sown immediately after being 

 gathered, produced few double-flowering plants ; while seed 

 three to four years old produced many. Wallflowers gave 

 similar results. 



Yet another fact may be mentioned which bears out the same 

 contention. It is found that old, strong root-stocks of Dahlias 

 produce strong growing plants, but they do not " double " well. 

 Heavy foliage and rich colouring are, as a rule, adverse to 

 doubling. 



The conclusion to be drawn from the above facts is that it is 

 not a rich soil which first induces doubling, but a poor one ; but 



