THE VARIETIES OF FERTILISATION. 321 



Comparing this plant witli i. fulgens, wliict is also qnite 

 sterile without aid, and, according to Gartner, is " quite 

 sterile with pollen from the same plant, though this pollen 

 is efficient on any other individual," * Mr. Darwin suc- 

 ceeded in raising self-fertilised plants by keeping the pollen 

 of a floAver in paper till the stigmas were ready, as it is 

 strongly protandrous. The heights of the offspring were as 

 100 : 127, and Mr. Darwin adds, " the self-fertilised plants 

 [in two out of four pots] were in eveiy respect very much 

 finer than the crossed plants." 



In the next generation he used pollen from a different 

 flower on the same plant to represent self-fertilisation. In 

 this case those " self-fertilised " were only 4 p.c. below the 

 crossed, the ratio being as 100 : 96. The conclusion, then, is 

 that self-fertilisation pure was the best ; intercrossing distinct 

 plants, less so ; and crossing on the same plant, the least. 



Bianthus, like Lobelia fulgens, is strongly protandrous ; 

 but in the third generation the proportional number of seeds 

 per capsule was as 100 : 125. " This anomalous result is 

 probably due to some of the fertilised plants having varied 

 so as to mature their pollen and stigmas more nearly at 

 the same time than is proper to the species " (p. 135). 

 Exactly so. 



The conclusion I would draw is, therefore, not that self- 

 fertilisation is per se in any way injurious, but that flowers 

 which are normally sterile, by having become so highly 

 differentiated through insect stimulation, do not now spon- 

 taneously set seed ; and self-fertilisation is not so efficient 

 as crossing. As soon, however, as the former process is 

 persevered with, signs are not wanting of nature's showing 

 even an eager response to it, till the results are often far 

 superior to those normally obtained by intercrossing. 

 * Cross and Self Fertilisation, eiG.,Tp.Vi9. 



