202 PETUNIA VIOLACEA. CHAP. VI. 



one lot being derived from plants self-fertilised for four genera- 

 tions and then crossed with a fresh stock ; to the second lot being 

 derived from plants of the same old stock intercrossed for five 

 generations ; and to the third lot being derived from plants self- 

 fertilised for five generations. All the capsules, some nearly 

 mature and some only half-grown, were gathered, counted, and 

 weighed from the ten finest plants in each of the three rows, of 

 which the measurements and weights have already been given. 

 The intercrossed plants, as we have seen, were taller and con- 

 siderably heavier than the plants of the other two lots, and they 

 produced a greater number of capsules than did even the 

 Westerham-crossed plants ; and this may be attributed to the 

 latter having grown more crowded and being in consequence less 

 branched. Therefore the average weight of an equal number of 

 capsules from each lot of plants seems to be the fairest standard 

 of comparison, as their weights will have been determined chiefly 

 by the number of the included seeds. As the intercrossed plants 

 were taller and heavier than the plants of the other two lots, it 

 might have been expected that they would have producedthe finest 

 or heaviest capsules ; but this was very far from being the case. 



The ten tallest Westerham-crossed plants produced 111 ripe 

 and unripe capsules, weighing 121 2 grains. Therefore 100 of 

 such capsules would have weighed 109 '18 grains. 



The ten tallest intercrossed plants produced 129 capsules, 

 weighing 76 45 grains. Therefore 100 of these capsules would 

 have weighed 59 '26 grains. 



The ten tallest self-fertilised plants produced only 44 capsules, 

 weighing 22 '35 grains. Therefore 100 of these capsules would 

 have weighed 50 '79 grains. 



From these data we get the following ratios for the fertility of 

 the three lots, as deduced from the relative weights of an equal 

 number of capsules from the finest plants in each lot : 



Westerham-crossed plants to self-fertilised 



plants as 100 to 46 



Westerham-crossed plants to intercrossed plants as 100 to 54 



Intercrossed plants to self-fertilised plants . as 100 to 86 



We here see how potent the influence of a cross with pollen 

 from a fresh stock has been on the fertility of plants self-fertilised 

 for four generations, in comparison with plants of the old stock 

 when either intercrossed or self-fertilised for five generations ; the 



