72 MIMULUS LUTEUS CHAP. III. 



The effects of a Cross with a distinct Stock. Some flowers on the 

 self-fertilised plants in Pot IV. in Table XIX. were fertilised 

 with their own pollen, and plants of the eighth self-fertilised 

 generation were thus raised, merely to serve as parents in the fol- 

 lowing experiment. Several flowers on these plants were allowed 

 to fertilise themselves spontaneously (insects being of course 

 excluded), and the plants raised from these seeds formed the 

 ninth self-fertilised generation ; they consisted wholly of the tall 

 white variety with crimson blotches. Other flowers on the 

 same plants of the eighth self-fertilised generation were crossed 

 with pollen taken from another plant of the same lot ; so that 

 the seedlings thus raised were the offspring of eight previous 

 generations of self-fertilisation with an intercross in the last 

 generation ; these I will call the intercrossed plants. Lastly, 

 other flowers on the same plants of the eighth self-fertilised 

 generation were crossed with pollen taken from plants which had 

 been raised from seed procured from a garden at Chelsea. The 

 Chelsea plants bore yellow flowers blotched with red, but differed 

 in no other respect. They had been grown out of doors, whilst 

 mine had been cultivated in pots in the greenhouse for the 

 last eight generations, and in a different kind of soil. The 

 seedlings raised from this cross with a wholly different stock 

 may be called the " Chelsea-crossed." The three lots of seeds 

 thus obtained were allowed to germinate on bare sand; and 

 whenever a seed in all three lots, or in only two, germinated at 

 the same time, they were planted in pots superficially divided 

 into three or two compartments. The remaining seeds, 

 whether or not in a state of germination, were thickly sown in 

 three divisions in a large pot, X., in Table XX. When the plants 

 had grown to their full height they were measured, as shown in 

 the following table ; but only the three tallest plants in each of 

 the three divisions in Pot X. were measured. 



In this table the average height of the twenty-eight Chelsea- 

 crossed plants is 21-62 inches; that of the twenty-seven inter- 

 crossed plants 12 2 ; and that of the nineteen self-fertilised 10 44. 

 But with respect to the latter it will be the fairest plan to strike out 

 two dwarfed ones (only 4 inches in height), so as not to exaggerate 

 the inferiority of the self-fertilised plants ; and this will raise the 

 average height of the seventeen remaining self-fertilised plants 

 to 11 '2 inches. Therefore the Chelsea-crossed are to the inter- 

 crossed in height as 100 to 56 ; the Chelsea-crossed to the self- 

 fertilised as 100 to 52 ; and the intercrossed to the self-fertilised 



