CHAP. III. CROSSED AND SELF-FERTILISED PI ANTS. 83 



and six others with pollen from a distinct plant growing within 

 the distance of a few feet. The covered plant was occasionally 

 shaken with violence, so as to imitate the effects of a gale of 

 wind, and thus to facilitate as far as possible self-fertilisation, 

 It bore ninety-two flowers (besides the dozen artificially ferti- 

 lised), and of these only twenty-four produced capsules ; whereas 

 almost all the flowers on the surrounding uncovered plants were 

 fruitful. Of the twenty-four spontaneously self-fertilised cap- 

 sules, only two contained their full complement of seed; six 

 contained a moderate supply; and the remaining sixteen ex- 

 tremely few seeds. A little pollen adhering to the anthers after 

 they had dehisced, and accidentally falling on the stigma when 

 mature, must have been the means by which the above twenty- 

 four flowers were partially self-fertilised ; for the margins of the 

 corolla in withering do not curl inwards, nor do the flowers in 

 dropping off turn round on their axes, so as to bring the pollen- 

 covered hairs, with which the lower surface is clothed, into con- 

 tact with the stigma by either of which means self- fertilisation 

 might be effected. 



Seeds from the above crossed and self-fertilised capsules, after 

 germinating on bare sand, were planted in pairs on the opposite 

 sides of five moderately-sized pots, which were kept in the green- 

 house. The plants after a time appeared starved, and were 

 therefore, without being disturbed, turned out of their pots, and 

 planted in the open ground in two close parallel rows. They 

 were thus subjected to tolerably severe competition with one 

 another ; but not nearly so severe as if they had been left in the 

 pots. At the time when they were turned out, their leaves were 

 between 5 and 8 inches in length, and the longest leaf on 

 the finest plant on each side of each pot was measured, with the 

 result that the leaves of the crossed plants exceeded, on an 

 average, those of the self- fertilised plants by '4 of an inch. 



In the following summer the tallest flower-stem on each plant, 

 when fully grown, was measured. There were seventeen crossed 

 plants ; but one did not produce a flower- stem. There were also, 

 originally, seventeen self-fertilised plants, but these had such 

 poor constitutions that no less than nine died in the course of 

 the winter and spring, leaving only eight to be measured, as in 

 the following table : 



G 2 



