Chap. VI. CROSS WITH A FRESH STOCK. 100 



The AYesterhani-crossed plants in height to the 

 self-fertilised as 100 to G6 



The Westerham-crossecl plants in height to the' 

 intercrossed as 100 to 108 



The intercrossed plants in height to the self- 

 fertilised as 100 to Gl 



We here see that the Westerham-crossed (the offspring of 

 plants self-fertilised for four generations and then crossed with a 

 fresh stock) have gained greatly in height, since they were first 

 measured, relatively to the plants self-fertilised for five genera- 

 tions. They were then as 100 to 91, and now as 100 to G6 in 

 huight. The intercrossed plants (i.e., those which had been in- 

 tercrossed for the last five generations) likewise exceed in 

 height the self-fertilised plants, as occurred in all the previous 

 generations with the exception of the abnormal plants of the 

 third generation. On the other hand, the "Westerham-crossed 

 plants are exceeded in height by the intercrossed ; and this is a 

 surprising fact, judging from most of the other strictly analogous 

 cases. But as the Westerham-crossed plants were still growing 

 vigorously, while the intercrossed had almost ceased to grow, 

 there can hardly be a doubt that if left to grow for another 

 month they would have beaten the intercrossed in height. That 

 they were gaining on them is clear, as when measured before they 

 were as 100 to 119, and now as only 100 to 108 in height. The 

 Westerham-crossed plants had also leaves of a darker green, and 

 looked altogether more vigorous than the intercrossed ; and what 

 is much more important, they produced, as we shall presently 

 see, much heavier seed-capsules. So that in fact the offspring 

 from the self-fertilised plants of the fourth generation crossed by 

 a fresh stock were superior to the intercrossed, as well as to the 

 self-fertilised plants of the fifth generation of which latter fact 

 there could not be the least doubt. 



These three lots of plants were cut down close to the ground 

 and weighed. The twenty-one Westerham-crossed plants weighed 

 32 ounces ; the twenty-two intercrossed plants, 31 ounces, and the 

 twenty-one self-fertilised plants 7i ounces. The following ratios 

 are calculated for an equal number of plants of each kind. But 

 as the self-fertilised plants were just beginning to wither, their 

 relative weight is here slightly too small ; and as the Westerham- 

 crossed were still growing vigorously, their relative weight 

 with time allowed would no doubt have greatly increased. 



