238 SUMMARY OF MEASUREMENTS. Chap. VII, 



CHAPTER VII. 



Summary op the Heights and Weights op the Crossed and 

 Self-fertilised Plants. 



Number of species and plants measured Tables given Preliminary 

 remarks on the offspring of plants crossed by a fresh stock Thirteen 

 cases specially considered The effects of crossing a self-fertilised 

 plant either by another self-fertilised plant or by an intercrossed plant 

 of the old stock Summary of the results Preliminary remarks on 

 the crossed and self-fertilised plants of the same stock The twenty- 

 six exceptional cases considered, in which the crossed plants did not 

 exceed greatly in height the self-fertilised Most of these cases 

 shown not to be real exceptions to the rule that cross-fertilisation 

 is beneficial Summary of results Relative weights of the crossed 

 and self-fertilised plants. 



The details which have been given under the head 

 of each species are so numerous and so intricate, that 

 it is necessary to tabulate the results. In Table A, the 

 number of plants of each kind which were raised from 

 a cross between two individuals of the same stock and 

 from self-fertilised seeds, together with their mean 

 or average heights at or near maturity, are given. In 

 the right-hand column, the mean height of the crossed 

 to that of the self-fertilised plants, the former being 

 taken as 100, is shown. To make this clear, it may 

 be advisable to give an example. In the first genera- 

 tion of Ipomoea, six plants derived from a cross 

 between two plants were measured, and their mean 

 height is 86 00 inches ; six plants derived from 

 flowers on the same parent-plant fertilised with their 

 own pollen were measured, and their mean height is 

 65 66 inches. From this it follows, as shown in the 

 right-hand column, that if the mean height of the 

 crossed plants be taken as 100, that of the self-fer- 



