310 UNIFOKM COLOUR OF THE FLOWERS CHAP. VIIL 



of the flowers on the self-fertilised plants of the fifth 

 generation. The flowers on the intercrossed plants of 

 the corresponding generation were mostly of the same 

 dull flesh colour, but not nearly so uniform as those on 

 the self-fertilised plants, some few being very pale, 

 almost white. The self-fertilised plants which grew in 

 a long row in the open ground were also remarkable for 

 their uniformity in height, as were the intercrossed 

 plants in a less degree, both lots being compared with 

 a large number of plants raised at the same time under 

 similar conditions from the self-fertilised plants of the 

 fourth generation crossed by a fresh stock. I regret 

 that I did not attend to the uniformity in height of 

 the self-fertilised seedlings in the later generations of 

 the other species. 



These few cases seem to me to possess much interest. 

 We learn from them that new and slight shades of 

 colour may be quickly and firmly fixed, independently 

 of any selection, if the conditions are kept as nearly 

 uniform as is possible, and no intercrossing be per- 

 mitted. With Mimulus, not only a grotesque style of 

 colouring, but a larger corolla and increased height of 

 the whole plant were thus fixed ; whereas with most 

 plants which have been long cultivated for the flower- 

 garden, no character is more variable than that of 

 colour, excepting perhaps that of height. From the 

 consideration of these cases we may infer that the 

 variability of cultivated plants in the above respects 

 is due, firstly, to their being subjected to somewhat 

 diversified conditions, and, secondly, to their being 

 often inter-crossed, as would follow from the free access 

 of insects. I do not see how this inference can be 

 avoided, as when the above plants were cultivated 

 for several generations under closely similar conditions, 

 and were intercrossed in each generation, the colour 



