OHAP. IX. SELF-STERILE PLANTS. 333 



capsules. Later in the season twelve other flowers on 

 these two plants were artificially self-fertilised ; but 

 they yielded only two capsules, containing three and 

 six seeds. It appears therefore that a lower tem- 

 perature than that of Brazil favours the self-fertility 

 of this plant, whilst a still lower temperature lessens it. 

 As soon as the two plants which had been covered by 

 the net were uncovered, they were visited by many 

 bees, and it was interesting to observe how quickly 

 they became, even the more sterile plant of the two, 

 covered with young capsules. On the following year 

 eight flowers on plants of the Brazilian stock of self- 

 fertilised parentage (i.e., grandchildren of the plants 

 which grew in Brazil) were again self-fertilised, and 

 produced five capsules, containing on an average 27*4 

 seeds, with a maximum in one of forty-two seeds ; so 

 that their self-fertility had evidently increased greatly 

 by being reared for two generations in England. On 

 the whole we may conclude that plants of the Brazilian 

 stock are much more self-fertile in this country than 

 in Brazil, and less so than plants of the English stock 

 in England ; so that the plants of Brazilian parentage 

 retained by inheritance some of their former sexual 

 constitution. Conversely, seeds from English plants 

 sent by me to Fritz Muller and grown in Brazil, were 

 much more self-fertile than his plants which had been 

 cultivated there for several generations ; but he informs 

 me that one of the plants of English parentage which 

 did not flower the first year, and was thus exposed for 

 two seasons to the climate of Brazil, proved quite self- 

 sterile, like a Brazilian plant, showing how quickly 

 the climate had acted on its sexual constitution. 



Abutilon darwinii. Seeds of this plant were sent 

 me by Fritz Muller, who found it, as well as some 

 other species of the same genus, quite sterile in its 



