308 UNIFORM COLOUR OF THE FLOWERS Chap. VIII. 



thorn; and the flowers on the several intercrossed 

 plants of the ninth generation differed considerably in 

 colour. On the other hand, the uniformity in colour 

 of the flowers on the plants of all the later self-fer- 

 tilised generations was quite surprising ; on a casual 

 inspection they might have been said to be quite alike, 

 but the crimson blotches were not of exactly the same 

 shape, or in exactly the same position. Both my 

 gardener and myself believe that this variety did 

 not appear amongst the parent-plants, raised from pur- 

 chased seeds, but from its appearance amongst both the 

 crossed and self-fertilised plants of the third and fourth 

 generations ; and from what I have seen of the variation 

 of this species on other occasions, it is probable that it 

 would occasionally appear under any circumstances. 

 We learn, however, from the present case that under 

 the peculiar conditions to which my plants were 

 subjected, this particular variety, remarkable for its 

 colouring, largeness of the corolla, and increased 

 height of the whole plant, prevailed in the sixth and 

 all the succeeding self-fertilised generations to the 

 complete exclusion of every other variety. 



Ipomoea purpurea. My attention was first drawn to 

 the present subject by observing that the flowers on all 

 the plants of the seventh self-fertilised generation were 

 of a uniform, remarkably rich, dark purple tint. The 

 many plants which were raised during the three suc- 

 ceeding generations, up to the last or tenth, all produced 

 flowers coloured in the same manner. They were 

 absolutely uniform in tint, like those of a constant 

 species living in a state of nature ; and the self-fertilised 

 plants might have been distinguished with certainty, 

 as my gardener remarked, without the aid of labels, 

 from the intercrossed plants of the later generations. 

 These, however, had more uniformly coloured flowers 



