14 INTRODUCTORY REMARKS. Chap. i. 



plants raised from the seeds remaining after the pairs 

 had been planted) unless the tallest plants on each 

 side seemed fairly to represent the average difference 

 between those on both sides. It has, however, some 

 great advantages, as sickly or accidentally injured 

 plants, or the offspring of ill-ripened seeds, are thus 

 eliminated. When the tallest plants alone on each side 

 were measured, their average height of course exceeds 

 that of all the plants on the same side taken together 

 But in the case of the much crowded plants raised 

 from the remaining seeds, the average height of the 

 tallest plants was less than that of the plants in pairs, 

 owing to the unfavourable conditions to which they 

 were subjected from being greatly crowded. For our 

 purpose, however, of the comparison of the crossed and 

 self-fertilised plants, their absolute height signifies 

 little. 



As the plants were measured by an ordinary English 

 standard divided into inches and eighths of an inch, I 

 have not thought it worth while to change the frac- 

 tions into decimals. The average or mean heights 

 were calculated in the ordinary rough method by 

 adding up the measurements of all, and dividing the 

 product by the number of plants measured ; the result 

 being here given in inches and decimals. As the 

 different species grow to various heights, I have always 

 for the sake of easy comparison given in addition the 

 average height of the crossed plants of each species 

 taken as 100, and have calculated the average height 

 of the self-fertilised plant in relation to this standard. 

 With respect to the crowded plants raised from the 

 ceeds remaining after the pairs had been planted, 

 and of which only some of the tallest on each side 

 were measured, I have not thought it worth while to 

 complicate the results by giving separate averages 



