Sprengel; Camerarius; Kolreuter 403 



my own observations on plants, guided to a certain extent by the 

 experience of the breeders of animals, I became convinced many years 

 ago that it is a general law of nature that flowers are adapted to be 

 crossed, at least occasionally, by pollen from a distinct plant 1 ." 



The experience of animal breeders pointed to the conclusion that 

 continual in-breeding is injurious. If this is correct, it raises the 

 question whether the same conclusion holds for plants. As most 

 flowers are hermaphrodite, plants afford much more favourable 

 material than animals for an experimental solution of the question, 

 what results follow from the union of nearly related sexual cells as 

 compared with those obtained by the introduction of new blood. 

 The answer to this question must, moreover, possess the greatest 

 significance for the correct understanding of sexual reproduction in 

 general. 



We see, therefore, that the problems which Darwin had before 

 him in his researches into the biology of flowers were of the greatest 

 importance, and at the same time that the point of view from which 

 he attacked the problems was essentially a teleological one. 



We may next inquire in what condition he found the biology of 

 flowers at the time of his first researches, which were undertaken 

 about the year 1838. In his autobiography he writes, — "During the 

 summer of 1839, and, I believe, during the previous summer, I was 

 led to attend to the cross-fertilisation of flowers by the aid of insects, 

 from having come to the conclusion in my speculations on the origin 

 of species, that crossing played an important part in keeping specific 

 forms constant 2 ." In 1841 he became acquainted with Sprengel's 

 work : his researches into the biology of flowers were thus continued 

 for about forty years. 



It is obvious that there could only be a biology of flowers after 

 it had been demonstrated that the formation of seeds and fruit in 

 the flower is dependent on pollination and subsequent fertilisation. 

 This proof was supplied at the end of the seventeenth century by R. J. 

 Camerarius (1665 — 1721). He showed that normally seeds and fruits 

 are developed only when the pollen reaches the stigma. The manner in 

 which this happens was first thoroughly investigated by J. G. Kolreuter 

 (1733 — 1806 3 ), the same observer to whom we owe the earliest experi- 

 ments in hybridisation of real scientific interest. Kolreuter mentioned 

 that pollen may be carried from one flower to another partly by 

 wind and partly by insects. But he held the view, and that was, 



1 Cross and Self fertilisation (1st edit.), p. 6. 



8 The Life and Letters of Charles Darwin, Vol. i. p. 90, London, 1888. 



3 Kolreuter, VorUiufige Nachricht von einigen das Geschlecht der Pflanzen betreffenden 

 Versuchen und Beobachtungen, Leipzig, 1761 ; with three supplements, 1703 — 66. Also, 

 jK&n. de Vacad. St Petersbourg, Vol. xv. 1809. 



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