I.] CROSS-FERTILISATION. 3 



from the stamens to the pistil, but in transferring it 

 from the stamens of one flower to the pistil of another. 

 Sprengel had indeed observed in more than one in- 

 stance that this was the case, but he did not altogether 

 appreciate the importance of the fact. 



Mr. Darwin, however, has not only made it clear 

 from theoretical considerations, but has also proved it, 

 in a variety of cases, by actual experiment. More 

 recently Fritz Miiller has even shown that in some 

 cases pollen, if placed on the stigma of the same 

 flower, has no more effect than so much inorganic 

 dust ; while, and this is perhaps even more extra- 

 ordinary, in others, the ppllen placed on the stigma of 

 the same flower acted on it like a poison. This he 

 observed in several species ; the flowers faded and fell 

 off, the pollen masses themselves, and the stigma in 

 contact with them, shrivelled up, turned brown, and 

 decayed ; while flowers on the same bunch, which were 

 left unfertilised, retained their freshness. 



The importance of this " cross-fertilisation," as it 

 maybe called, in contradistinction to "self-fertilisa- 

 tion," was first conclusively proved by Mr. Darwin in 

 his remarkable memoir on Primula (Linnean Journal, 

 1862), and he has since illustrated the same rule by 

 researches on Orchids, Linum, Lythrum, and a variety 

 of other plants. The new impulse thus given to the 

 study of flowers has been followed up in this country 

 by Hooker, Ogle, Bennett, and other naturalists, and 

 on the Continent by Axell, Delpino, Hildebrami, 

 Kerner, F. Miiller, and especially by Dr. H. Muller. 

 who has brought together the observations of others, 

 and added to them an immense number of his own. 



B 2 



