43 History of the Sexual Theory. [BOOK in. 



respecting the conditions under which the production of hy- 

 brids is possible, the results of crossing, and the causes of 

 failure. A special interest attaches to his mixed and com- 

 pound hybrids, to his experiments on the various degrees of 

 influence which foreign pollen exercises on the behaviour of 

 the female organ, and the connection of this point with the 

 formation of varieties. It is impossible to give a more distinct 

 account of Gartner's results without entering into discussions 

 which would exceed the limits of a historical survey. It is the 

 less necessary to do so, since Na'geli undertook in 1865 to 

 give a summary view of all the important results to be found 

 in the wealth of material supplied by Koelreuter, Herbert and 

 Gartner 1 . Gartner's experiments in hybridisation were con- 

 ducted at Calw in Wiirtemberg, the place where Koelreuter 

 had made his in 1762 and 1763. And thus it was in two 

 small cities of Wiirtemberg that the foundations of the sexual 

 theory were laid and the theory itself perfected, as far as it 

 could be by experiment only, by three of the most eminent 

 among observers. Camerarius in Tubingen, Koelreuter and 

 K. F. Gartner in Calw contributed so largely to the empirical 

 establishment of the theory, that all that was done by others 

 would seem of small importance, if artificial pollination only 

 were in question. But Koelreuter was imperfectly acquainted 

 with the methods by which pollination is usually effected in 

 nature ; Sprengel was the first who saw into all their more 

 important relations, and the fact must not be concealed, that 

 Gartner in regarding Konrad Sprengel's observations as un- 

 worthy of serious consideration, neglected the most fruitful 

 source of new and magnificent results. His careful study of 

 the secreting of nectar and of the sensitiveness of the organs of 

 fertilisation, and his many observations on other biological re- 

 lations in flowers, would have found their natural termination, 

 if he had connected them at all points with Sprengel's general 



1 See also Sachs, ' Lehrbuch der Botanik,' Leipzig, 1874. 



