42 IPOMCEA PUKPUEEA. CHAP. II. 



over the offspring from flowers fertilised with their 

 own pollen. I procured some fresh seed and raised 

 two plants, which were covered with a net ; and several 

 of their flowers were crossed with pollen from a dis- 

 tinct flower on the same plant. Twenty-nine capsules 

 thus produced contained on an average 4 -86 seeds per 

 capsule ; and 100 of these seeds weighed 36 77 grains. 

 Several other flowers were fertilised with their own 

 pollen, and twenty-six capsules thus produced con- 

 tained on an average 4 - 42 seeds per capsule; 100 of 

 which weighed 42 61 grains. So that a cross of this 

 kind appears to have increased slightly the number of 

 seeds per capsule, in the ratio of 100 to 91 ; but these 

 crossed seeds were lighter than the self-fertilised in the 

 ratio of 86 to 100. I doubt, however, from other 

 observations, whether these results are fully trust- 

 worthy. The two lots of seeds, after germinating on 

 sand, were planted in pairs on the opposite sides of 

 nine pots, and were treated in every respect like the 

 plants in the previous experiments. The remaining 

 seeds, some in a state of germination and some not 

 so, were sown on the opposite sides of a large pot 

 (No. X.) ; and the four tallest plants on each side of 

 this pot were measured. The result is shown in 

 Table XII. 



The average height of the thirty-one crossed plants is 

 73 23 inches, and that of the thirty-one self-fertilised 

 plants 77-41 inches; or as 100 to 106. Looking to 

 each pair, it may be seen that only thirteen of the 

 crossed plants, whilst eighteen of the self-fertilised 

 plants exceed their opponents. A record was kept with 

 respect to the plant which flowered first in each pot ; 

 and only two of the crossed flowered before one of the 

 self-fertilised in the same pot ; whilst eight of the self- 

 fertilised flowered first. It thus appears that the 



