80 MIMULUS LUTEUS. Chap. III. 



how far it was at first used either for crossing or self- 

 fertilisation. In the fifth generation most of the 

 self-fertilised plants, and in the sixth and all the 

 succeeding generations every single plant consisted of 

 this variety ; and this no doubt was partly due to its 

 great and increasing self-fertility. On the other 

 hand, it disappeared from amongst the crossed plants 

 in the later generations ; and this was probably 

 due to the continued intercrossing of the several 

 plants. From the tallness of this variety, the self- 

 fertilised plants exceeded the crossed plants in height 

 in all the generations from the fifth to the seventh 

 inclusive; and no doubt would have done so in the 

 later generations, had they been grown in competition 

 with one another. In the fifth generation the crossed 

 plants were in height to the self-fertilised, as 100 to 

 126 ; in the sixth, as 100 to 147 ; and in the seventh 

 generation, as 100 to 137. This excess of height may 

 be attributed not only to this variety naturally growing 

 taller than the other plants, but to its possessing a 

 peculiar constitution, so that it did not suffer from 

 continued self-fertilisation. 



This variety presents a strikingly analogous case to 

 that of the plant called the Hero, which appeared in 

 the sixth self-fertilised generation of Ipomoea. If 

 the seeds produced by Hero had been as greatly in 

 excess of those produced by the other plants, as was the 

 case with Mimulus, and if all the seeds had been 

 mingled together, the offspring of Hero would have 

 increased to the entire exclusion of the ordinary 

 plants in the later self-fertilised generations, and from 

 naturally growing taller would have exceeded the 

 crossed plants in height in each succeeding generation. 



Some of the self-fertilised plants of the sixth gene- 

 ration were intercrossed, as were some in the eighth 



