8 INTRODUCTION 



that which has been blown away, and is drifting in the air.' This pollen ' is very 

 buoyant, and is readily carried away by the slightest breath of wind.' ' Both the 

 anthers and the stigmas must be exposed to the air, so that the wind may carry 

 the pollen from the former to the latter, and the stigmas must be a considerable 

 size, because if very small they would but rarely receive pollen.' 



Sprengel thus set forth the main ideas of flower pollination, and laid a founda- 

 tion which was not to be built upon till two generations later. His investigations 

 received little attention, or were made light of, and then passed wholly into oblivion, 

 because of the influence of Linnaeus and his successors, who regarded the building 

 up of systematic botany, the description of species, as the real end of botany. It 

 was only on the appearance of Charles Darwin's^ work on the Origin of Species 

 (1859) that flower pollination came into prominence, and that Sprengel's work 

 received due recognition ^ 



It is true that Sprengel came very near understanding the use of cross- 

 pollination for plants; but he does not express it. He is content to establish 

 the fact of crossing, and to add the remark: 'As very many flowers are of separate 

 sexes, and probably quite as many of the hermaphrodite ones are dichogamous, 

 // seevis thai Nature is unwilling that any flower should be fertilized by its own pollen^ 

 ('Entd. Geh.,'p. 43). 



Thomas Andrew Knight took a step further in the interpretation of these 

 phenomena^. As early as 1799 he based upon the results of cross-fertilizations 

 of cultivated plants the conclusion that no plant fertilizes itself through many 

 generations. 



In 1858 Darwin proved that in certain Papilionaceae, which he protected 

 from visits of insects in Sprengel's way by means of a net, the formation of seeds 

 is not so vigorous as when there is cross-fertilization. Darwin's work on the 



1 Charles Robert Darwin was born at Shrewsbury on February 12, 1809. In 1825 he entered 

 the University of Edinburgh; he completed his studies at Cambridge, where he graduated in 1831. 

 Subsequently he accompanied the expedition of Captain Fitzroy in the capacity of naturalist ; visited 

 Brazil, the west coast of South America, and the islands of the Pacific. In 1842 he inherited the 

 property of Down near Beckenham, where he devoted himself to his studies till his death 

 (April 19, 1882). 



^ In 'Nature,' xxix, H. A. Hagen opposes the current view that Ch. K. Sprengel's work had 

 remained wholly unknown till brought to light again by Charles Darwin. He makes out that at 

 least in Germany Sprengel's discoveries were well known to every naturalist throughout the century, 

 and that between 1830 and 1840 Sprengel's doctrines were taught at every Prussian University. 

 Fritz Miiller (op. cit.) disputed Hagen's contention because he himself had heard hardly a word 

 about Sprengel from Lichtenstein, or Knuth, or Erichson at Berlin in 1841, or from Hornschuch at 

 Greifswald in 1842 ; and moreover his brother Hermann had heard nothing of Sprengel in Halle in 

 1848. K. Mobius (op. cit.) heard Schultz-Schultzenstein discuss Sprengel's theories in Berlin 

 in 1850. H. A. Hagen (op. cit.) remarks that the well-kno%vn Berlin physician E. L. Heim 

 discusses Sprengel's doctrines in spirited fashion in his diary, and states from personal recollection 

 that Sprengel's discoveries were known in Berlin to Linde, Lichtenstein, Klug, and Erichson, in Bonn 

 to Treviranus, in Breslau to Nees von Esebeck. Also according to him these doctrines were not 

 forgotten in England, for Sprengel's views are considered in all of the seven editions of Kirby and 

 Spence's 'Introduction to Entomology' that appeared between 181 5 and 1867, the last issue 

 comprising 13,000 copies. (From Koehne in Bot. Jahrb., Leipzig, i, 1885, pp. 731, 732.) 



* Knight (i 758-1838) was for many years President of the Horticultural Society of London. 

 See Ostwald's ' Klassiker,' No. Ixii, which include six treatises by Knight on plant physiology. 



