404 The Biology of Flowers 
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 und in der 
Befruchtung 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 und 
Beobachtungen wber die Befruchtungsorgane der vollkommeneren 
Gewdichse und iiber die natiirliche und kiinstliche Befruchtung 
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 Kélreuter 
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.” 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. 
