Chap. IV. CKOSS WITH A FRESH STOCK. 115 



the open ground flowered profusely, and the flowers were inces- 

 santly visited by bees, and certainly thus intercrossed. The 

 manner in which several plants in the previous experiments 

 continued to be almost sterile as long as they were covered by a 

 net, but set a multitude of capsules immediately that they were 

 uncovered, proves how effectually the bees carry pollen from 

 plant to plant. My gardener gathered, at three successive 

 times, an equal number of ripe capsules from the plants of the 

 three lots, until he had collected forty-five from each lot. It is 

 not possible to judge from external appearance whether or not a 

 capsule contains any good seeds ; so that I opened all the cap- 

 sules. Of the forty-five from the English-crossed plants, four 

 were empty ; of those from the intercrossed, five were empty ; 

 and of those from the self-fertilised, nine were empty. The 

 seeds were counted in twenty-one capsules taken by chance out 

 of each lot, and the average number of seeds in the capsules 

 from the English-crossed plants was 67 ; from the intercrossed, 

 6 ; and from the self-fertilised, 48 ' 52. It therefore follows that 



Seeds. 



The forty-five capsules (the four empty ones in- 

 cluded) from the English-crossed plants contained 2747 



The forty-five capsules (the five empty ones in- 

 cluded) from the intercrossed plants contained . 2240 



The forty-five capsules (the nine empty ones in- 

 cluded) from the self-fertilised plants contained . 1746*7 



The reader should remember that these capsules are the pro- 

 duct of cross-fertilisation, effected by the bees; and that the 

 difference in the number of the contained seeds must depend on 

 the constitution of the plants ; that is, on whether they were 

 derived from a cross with a distinct stock, or from a cross 

 between plants of the same stock, or from self-fertilisation. 

 From the above facts we obtain the following ratios : 



Number of seeds contained in an equal nurr^r of naturally 

 fertilised capsules produced 

 By the English-crossed and self-fertilised plants, as 100 to 63 

 By the English-crossed and intercrossed plants, .s 100 to 81 

 By the intercrossed and selMertilised plants, as 100 to 78 



But to have ascertained the productiveness of the three lots 

 of plants, it would have been necessary to know how many 

 capsules were produced by the same number of plants. The 



I 2 



