CHAP. VII. SUMMARY OF MEASUREMENTS. 239 



tilised plants is 76. The same plan is followed with 

 all the other species. 



The crossed and self-fertilised plants were generally 

 grown in pots in competition with one another, and 

 always under as closely similar conditions as could 

 be attained. They were, however, sometimes grown in 

 separate rows in the open ground. With several of 

 the species, the crossed plants were again crossed, and 

 the self-fertilised plants again self-fertilised, and thus 

 successive generations were raised and measured, as 

 may be seen in Table A. Owing to this manner of 

 proceeding, the crossed plants became in the later 

 generations more or less closely inter-related. The 

 later generations of Mimulus are not included, as a 

 new tall variety then prevailed on one side alone, so 

 that a fair comparison between the two sides was no 

 longer possible. With Ipomoea the variety Hero has 

 been excluded for nearly the same reason. 



In Table B the relative weights of the crossed and 

 self-fertilised plants, after they had flowered and had 

 been cut down, are given in the few cases in which 

 they were ascertained. The results are, I think, more 

 striking and of greater value as evidence of constitu- 

 tional vigour than those deduced from the relative 

 heights of the plants. 



The most important table is that of C, as it includes 

 the relative heights, weights, and fertility of plants 

 raised from parents crossed by a fresh stock (that is, by 

 non-related plants grown under different conditions), 

 or by a distinct sub-variety, in comparison with self- 

 fertilised plants, or in a few cases with plants of the 

 same old stock intercrossed during several generations. 

 The relative fertility of the plants in this and the 

 other tables will be more fully considered in a future 

 chapter. 



