260 SUMMARY OF MEASUREMENTS. CHAP. VIL 



self-fertilised plants of the sixth generation had become 

 much more fertile than the intercrossed plants, judging 

 by the number of capsules spontaneously produced, in 

 the ratio of 147 to 100. This variety, which as we 

 have seen appeared amongst the plants of the fourth 

 self-fertilised generation, resembles in almost all its 

 constitutional peculiarities the variety called Hero, 

 which appeared in the sixth self- fertilised generation 

 of Ipomoea. No other such case, with the partial ex- 

 ception of that of Nicotiana, occurred in my experi- 

 ments, carried on during eleven years. 



Two plants of this variety of Mimulus, belonging to 

 the sixth self-fertilised generation, and growing in 

 separate pots, were intercrossed ; and some flowers on 

 the same plants were again self-fertilised. From the 

 seeds thus obtained, plants derived from a cross 

 between the self-fertilised plants, and others of the 

 seventh self-fertilised generation, were raised. But 

 this cross did not do the least good, the intercrossed 

 plants being inferior in height to the self-fertilised, in 

 the ratio of 100 to 110. This case is exactly parallel 

 with that given under Ipomoea, of the grandchildren 

 of Hero, and apparently of its great-grandchildren ; 

 for the seedlings raised by intercrossing these plants 

 were not in any way superior to those of the cor- 

 responding generation raised from the self-fertilised 

 flowers. Therefore in these several cases the crossing 

 of plants, which had been self-fertilised for several 

 generations and which had been cultivated all the 

 time under as nearly as possible the same conditions, 

 was not in the least beneficial. 



Another experiment was now tried. Firstly, plants 

 of the eighth self-fertilised generation were again 

 self-fertilised, producing plants of the ninth self- 

 lertilised generation. Secondly, two of the plants of the 



