820 THE STRUCTURE OF FLOWERS. 



the strongly protandrous Carnation can be made to be 

 liigbly self-fertile, as Mr. Darwin showed; and Linum perenne 

 can have its pollen so modified as to set seed abundantly in 

 the same flower, as occurred w^ith Mr. Meehan in Philadephia, 

 though it was physiologically impotent in England. 



It is, in fact, so to say a mere accident that mechanical 

 and physiological barriers exist at all ; and it is only by 

 experiment that one can discover whether a flower so 

 conditioned may not be really capable of self-fertilisation all 

 the time. Indeed, Mr. Darwin's experiments have abundantly 

 shown that self-fertilising properties are quickly reacquired, 

 whenever the process is persevered with. For example, 

 E sells choUzia Ccdifornica was "absolutely self -sterile " in 

 Brazil. Mr. Darwin, however, by self-fertilising it in Eng- 

 land, raised the fertility in two generations to nearly 87 p.c. 



When he asserts that his artificial crossings could not have 

 increased the vigour of the offspring, and therefore all differ- 

 ences must be attributed to the inferiority of the self-fer- 

 tilised, this argument would apply to a certain number of his 

 experiments in different degrees, viz., with plants normally 

 self-sterile ; but he ignores the fact that, as soon as he tried 

 to raise a stock of self-fertilised plants, the latter steadily 

 gained upon the offspring of the crossed, till they equalled 

 or surpassed them, or else would have done so had the 

 experiments been continued. 



Thus, with regard to Lohelia ramosa, the ratio of heights 

 of the " intercrossed " to the " self-fertilised " offspring of 

 first generation was 100 : 82 ; and the proportion of seeds as 

 100 : 60. In the second year, those growing under what he 

 had proved to be the most disadvantageous condition for 

 self-fertilised seedlings, namely, being crowded, the ratio 

 of the heights became as 100 : 88-3. The experiment, 

 unfortunately, was not continued further. 



