150 THE OLDER HYBRIDISTS 



Between 1760 and 1766 Joseph Gottleib Kolreuter 

 carried out the first series of systematic experiments 

 in plant hybridization which had ever been under- 

 taken. These experiments not only established with 

 certainty for the first time the fact that the seeds of 

 plants are produced by a sexual process comparable 

 with that known to occur in animals, but also led to a 

 knowledge of the general behaviour of hybrid plants, 

 which was scarcely bettered until Mendel made his 

 observations a century afterwards. 



Kolreuter found that the hybrid offspring of two 

 different plants generally took as closely after the 

 plant which yielded the pollen as after that upon 

 which the actual hybrid seed was born. Indeed, he 

 found that it made little or no difference to the ap- 

 pearance of the hybrid which of the parental species 

 was the pollen-parent (male), and which the seed- 

 parent (female) that is to say, in the case of plants 

 the result of reciprocal crosses is usually identical. 

 Thus, for the first time it was definitely shown that 

 the pollen-grain plays just as important a part in 

 determining the characters of the offspring as does the 

 ovule which the pollen-grain fertilizes. This was a 

 wholly novel idea in Kolreuter's time, and the fact was 

 scarcely credited by his contemporaries. 



Kolreuter had no means of discovering that the 

 contents of a single pollen-grain unite with the con- 

 tents of a single ovule in fertilization. But he ascer- 

 tained by experiments that more than thirty seeds 

 might be made to ripen by the application of between 

 fifty and sixty pollen-grains to the stigma of a par- 



