Increase in Variability m One Direction. 13 



sowings repeated year after year avail nothing if chance 

 does not play its part. Anemone coronaria plena arose 

 in the nurseries of Williamson in England as a single 

 plant, which exhibited a slight petaloid broadening of one 

 of the stamens.^ From the seed of this specimen a race 

 has been started, the flowers of which became fully 

 double in the course of a few generations. The double 

 varieties of roses. Campanulas, and many other garden 

 plants have arisen in the same way. I saw a bed of 

 mignonette {Reseda odorata) some of which had double 

 spikes, in a nursery at Erfurt. The spikes were fasciated, 

 the flowers were broader and the whole plant fuller, more 

 compact and handsomer than the species. The plants of 

 this bed had been produced from the seed of two fasciated 

 specimens which had accidentally appeared the year be- 

 fore. The normal were weeded out and the abnormal 

 saved and allowed to set seed with a view to putting a 

 new variety on the market. 



In cases such as this, selection has a twofold object. 

 In the first place the variety must be isolated, — that is 

 purged of the impurities resulting from free crossing. 

 It must also be actually improved by selection. The first 

 indications of doubling are, as we have seen, single super- 

 numerary petals, or in composites single supernumerary 

 ray florets on the disc ; the first indication of a new color 

 is often very pale ; slit leaves and petals are indicated by 

 quite small invaginations, combs (Vol. I, p. 191) appear 

 as small outgrowths. All these qualities had to be im- 

 proved by selection up to the level of the mean of the 

 character and then even perhaps beyond. 



An improvement of this kind, when once started, is 

 effected not only rapidly but with increasing swiftness. 



Darwin, Inc. cif., TT, p. 269. 



