CHAP. VI. CROSS WITH A FRESH STOCK. 197 



Seeds from the Westerham-crossecl capsules to 

 those from the capsules of the fifth self-fer- 

 tilised generation, in weight . . .as 100 to 48 



Seeds from the Westerham-erossed capsules to 

 those from the capsules of the fifth intercrossed 

 generation as 100 to 66 



Seeds from the intercrossed to those from the 

 self-fertilised capsules . . . . as 100 to 72 



So that a cross with pollen from a fresh stock greatly increased 

 the productiveness of the flowers on plants which had been self- 

 fertilised for the four previous generations, in comparison not 

 only with the flowers on the same plants self-fertilised for the fifth 

 time, but with the flowers on the crossed plants crossed with 

 pollen from another plant of the same old stock for the fifth 

 time. 



These three lots of seeds were placed on sand, and were 

 planted in an equal state of germination in seven pots, each made 

 tripartite by three superficial partitions. Some of the remaining 

 seeds, whether or not in a state of germination, were thickly 

 sown in an eighth pot. The pots were kept in the greenhouse, 

 and the plants trained up sticks. They were first measured to 

 the tops of their stems when coming into flower ; and the twenty- 

 two Westerham-erossed plants then averaged 25 51 inches ; the 

 twenty-three intercrossed plants 30 '38; and the twenty-three 

 self-fertilised plants 23 '40 inches in height. We thus get the 

 following ratios : 



The Westerham-erossed plants in height to the 

 self-fertilised as 100 to 91 



The Westerham-erossed plants in height to the 

 intercrossed as 100 to 119 



The intercrossed plants in height to the self- 

 fertilised . . . . . . . as 100 to 77 



These plants were again measured when their growth appeared 

 on a casual inspection to be complete. But in this I was mis- 

 taken, for after cutting them down, I found that the summits 

 of the stems of the Westerham-erossed plants were still growing 

 vigorously; whilst the intercrossed had almost, and the self- 

 fertilised had quite completed their growth. Therefore I do 

 not doubt, if the three lots had been left to grow for another 

 month, that the ratios would have been somewhat different 



