CHAP. VIII. OF THE CROSSED PLANTS. 287 



over the crossed in the start for the race. N evertheless 

 they were easily beaten (as may be seen under the 

 head of Mimulus) when the crossed seeds were sown 

 two whole days after the self-fertilised. But when the 

 interval was four days, the two lots were nearly equal 

 throughout life. Even in this latter case the crossed 

 plants still possessed an inherent advantage, for after 

 both lots had grown to their full height they were 

 cut down, and without being disturbed were transferred 

 to a larger pot, and when in the ensuing year they 

 had again grown to their full height they were 

 measured ; and now the tallest crossed plants were to 

 the tallest self-fertilised plants in height as 100 to 75, 

 and in fertility (i.e., by weight of seeds produced by an 

 equal number of capsules from both lots) as 100 to 34. 

 My usual method of proceeding, namely, to plant 

 several pairs of crossed and self-fertilised seeds in an 

 equal state of germination on the opposite sides of the 

 same pots, so that the plants were subjected to 

 moderately severe mutual competition, was I think 

 the best that could have been followed, and was a fair 

 test of what occurs in a state of nature. For plants 

 sown by nature generally come up crowded, and are 

 almost always exposed to very severe competition 

 with one another and with other kinds of plants. This 

 latter consideration led me to make some trials, chiefly 

 but not exclusively with Ipomcea and Mimulus, by 

 sowing crossed and self-fertilised seeds on the opposite 

 sides of large pots in which other plants had long been 

 growing, or in the midst of other plants out of doors. 

 The seedlings were thus subjected to very severe 

 competition with plants of other kinds; and in all 

 such cases, the crossed seedlings exhibited a great 

 superiority in their power of growth over the self- 

 fertilised. 



