4o6 History of the Sexual Theory. [Book hi. 



5. Further development of the sexual theory by Joseph 

 Gottlieb Koelreuter, and Konrad Sprengel. 



1761-1793- 



Camerarius had shown by experiment that the co-operation 

 of the pollen is indispensable to the production in plants of 

 seeds containing an embryo, and later observers had confirmed 

 the fact of sexuality by further and varied experiments. The 

 next step in the strict scientific investigation of the matter was 

 to determine by the same method of experiment the share of 

 each principle, the male and the female, in the formation of 

 the new plant which resulted from the sexual act. When 

 pollen and ovule belong to the same individual plant, the 

 offspring assumes the same form and the question remains 

 undecided. It was necessary to bring together the pollen and 

 ovule of different plants ; this must show whether some 

 characters are derived to the offspring from the pollen, and 

 others from the ovule, and what the characters are which are 

 thus distinguished, supposing of course that such a union of 

 different forms is possible. The answer to these questions 

 could only be obtained by experiment, that is by artificial 

 hybridisation ; for until hybrid forms had actually been 

 produced in this manner, it must be quite unsafe to assume 

 that certain wild plants owed their origin to cross-fertilisation. 



Camerarius had already raised the question in his letter, 

 whether cross-fertilisation in plants is possible, and had added 

 another, whether the progeny varies from its parents (an et 

 quam mutatus inde prodeat foetus). Bradley is our authority 

 for the statement that a gardener in London had obtained a 

 hybrid between Dianthus caryophyllus and Dianthus barbatus 

 by artificial means as early as 17 19; but Koelreuter 1 was 



1 Joseph Gottlieb Koelreuter was born at Sulz on the Neckar in 1733, 

 and died at Carlsruhe in 1806, where he was Professor of Natural History, 

 and from 1768 to 1786 Director also of the Botanic and Grand-ducal 

 Gardens. On giving up the latter position he continued his experiments in 

 his own small garden till the year 1790. Karl Friedrich Gartner in his work 



