METAMORPHOSES OF INFLORESCENCES AND FLOWERS. 99 



the pistil remaining in a normal condition so that a completely" double " 

 Composite is entirely female, and can only set seed by the aid of pollen 

 from some more or less unchanged flowers. 



In Centaureas, however, the trumpet-like ray-florets are so much 

 enlarged that the pistil is now sacrificed as well as the stamens ; hence 

 the ray-florets are all neuter and functionless, except so far as they 

 enhance the attractiveness of the head. 



Probable Causes of " Doubling."— The primary cause of doubling 

 appears to be any check to the vital activities of a plant ; the principal 

 one, at least in the wild state, being a very poor dry soil and a dry 

 atmosphere. 



Darwin wrote as follows in 1843 to the " Gardeners' Chronicle " about 

 some plants of Gentiana Amarella : " The plants grow on a very hard 

 bare chalk bank, where it was surprising that anything could grow at all. 

 I found on an adjoining field of wretchedly sterile clay great numbers 

 of Banimculus repens producing semi-double flowers. The partial or 

 entire sterility of double flowers is generally attributed to their doubleness, 

 but is not this putting the effect before the cause ? It is well known 

 that plants when placed out of their natural conditions become sterile. 

 Linna?us has remarked that most Alpine plants* when cultivated in the 

 lowlands, are rendered quite sterile. 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? " 



Observations on the conditions associated with doubling seem to 

 corroborate this idea of Darwin's, for several instances have been 

 recorded of wild plants becoming double under impoverished conditions 

 of the sort mentioned. 



A drier climate than that of England probably accounts for more 

 double flowers being raised on the Continent than in England, as I 

 learnt from the late Mr. Bull. 



The Eev. C. Wolley-Dod and others have pointed out that the wild 

 English Daffodil ofcen becomes double when transferred to gardens, 

 but that in his own cold and wet soil double-flowering plants tend to 

 become single. Similarly, in a garden in Italy the owner could " keep no 

 single Daffodils for more than a year or two, as they all turn double." 

 The change of climate and soil appears to be the cause of doubling in 

 these cases. Another writes saying that "the Tenby Daffodils (Narcissus 

 obvallaris) have nearly all become double in this dry sandy soil (near 

 Hitchin). N. ' Golden Spur' has also become double this season, 1904." 

 Early double Tulips are best associated with a dry poor soil, as it is 

 conducive to doubling, according to Mr. Houston. 



Mr. Douglas's experience with Carnations is that potted plants produce 

 more " doubles " than those grown in the open. " The finest lot of 

 choice varieties was in a hot dry season." "In a German establishment 

 thousands of flower-pots about five or six inches in diameter were arranged 

 on a wooden staging fully exposed to the open air, and I was also informed 

 that it was necessary to grow the plants in this way, to make sure of the 

 seed producing a large percentage of double flowers." Mr. Douglas also 

 observes that "the pink has a greater tendency to produce double 

 flowers than any other plant known to me, and certainly the tendency is 



