404 The Biology of Floivers 



indeed, the natural assumption, that self-fertilisation usually occurs 

 in a flower, in other words that the pollen of a flower reaches the stigma 

 of the same flower. He demonstrated, however, certain cases in which 

 cross-pollination occurs, that is in which the pollen of another flower 

 of the same species is conveyed to the stigma. He was familiar with 

 the phenomenon, exhibited by numerous flowers, to which Sprengel 

 afterwards applied the term Dichogamy, expressing the fact that the 

 anthers and stigmas of a flower often ripen at different times, a 

 peculiarity which is now recognised as one of the commonest means 

 of ensuring cross-pollination. 



With far greater thoroughness and with astonishing power of 

 observation C. K. Sprengel (1750-1816) investigated the conditions 

 of pollination of flowers. Darwin was introduced by that eminent 

 botanist Robert Brown to Sprengel's then but little appreciated 

 work, — Das entdeckte Geheimniss der Natur im Bau mid in der 

 Befruchtimg der Blumen (Berlin, 1793) ; this is by no means the 

 least service to Botany rendered by Robert Brown. 



Sprengel proceeded from a naive teleological point of view. He 

 firmly believed "that the wise Author of nature had not created a 

 single hair without a definite purpose." He succeeded in demon- 

 strating a number of beautiful adaptations in flowers for ensuring 

 pollination ; but his work exercised but little influence on his con- 

 temporaries and indeed for a long time after his death. It was 

 through Darwin that Sprengel's work first achieved a well deserved 

 though belated fame. Even such botanists as concerned themselves 

 with researches into the biology of flowers appear to have formerly 

 attached much less value to Sprengel's work than it has received 

 since Darwin's time. In illustration of this we may quote C. F. 

 Gartner whose name is rightly held in the highest esteem as that of 

 one of the most eminent hybridologists. In his work Versuche mid 

 Beobachtungen iiber die Befruchtungsorgane der vollkommeneren 

 Gewachse und iiber die natiirliche und kimstliche Befruchtmig 

 durch den eigenen Pollen he also deals with flower-pollination. 

 He recognised the action of the wind, but he believed, in 

 spite of the fact that he both knew and quoted Kblreuter 

 and Sprengel, that while insects assist pollination, they do so 

 only occasionally, and he held that insects are responsible for the 

 conveyance of pollen ; thorough investigations would show " that 

 a very small proportion of the plants included in this category 

 require this assistance in their native habitat 1 ." In the majority of 

 plants self-pollination occurs. 



Seeing that even investigators who had worked for several decades 

 at fertilisation-phenomena had not advanced the biology of flowers 



1 Gartner, Versuche und Beobachtungen..., p. 335, Stuttgart, 1844. 



