SEVENTEENTH AND EIGHTEENTH CENTURIES 155 

 made professor in natural history and curator of the botanical gardens at 

 Karlsruhe. He died in 1806. Before his appointment to the professorship he 

 had already published the first series of notes in which he recorded the 

 results of his experiment with the artificial fertilization of plants. As we 

 have seen, Camerarius was the first to experiment in this field. Linnxus fol- 

 lowed in his footsteps, carrying out, it will be remembered, the hybridization 

 of plants, but not being otherwise an experimental naturalist-worker in the 

 true sense. 



Koelreuter s experiments in plant-life fertilization 

 KoELREUTER was the first who exclusively applied himself to experimenting 

 with the cultivation of plants with a view to explaining their fertilization 

 and development. To begin with he investigated the act of fertilization 

 itself; he examined the pollen under the microscope and came to the con- 

 clusion that its fertilizing property is due to an oily fluid that it secretes; 

 on the stigma of the pistil he found a similar fluid and concludes therefrom 

 that fertilization consists in a union of these fluids, just as an acid and a base 

 form a salt. Of greater value than these speculations are his careful observa- 

 tions of the method of transmitting the pollen; he is the first to explain 

 clearly that certain flowers are invariably fertilized by insects, and he also 

 pointed out the part played by the wind in the fertilization of other forms. 

 Of greatest interest, however, are his investigations in connexion with hy- 

 brid formations, a problem to which he eventually devoted all his attention. 

 In this sphere he paved the way for a field of research that, as is well known, 

 has at the present day attracted the interest of both the scientific world 

 and the public more than most others. To start with, for a number of years 

 he crossed different types of tobacco-plants with one another, afterwards, 

 however, proceeding to other plant genera: pinks, aquilegia, verbascum, and 

 others. Moreover, he was able to vary his experiments and to observe the 

 results thereof; he carefully compared the hybrids with the parent individ- 

 uals and noted similarities and dissimilarities between them; he mated the 

 hybrids with their parent species and observed the reversion to similarity 

 with the latter; he fertilized the hybrids with one another and obtained 

 results that foreshadowed Mendel's famous observations; he likewise even 

 noted cases which would be regarded at the present day as mutations. How- 

 ever, he naturally did not succeed in utilizing theoretically the results of 

 his experiments; besides, his ideas of the actual essence of fertilization were 

 all too vague — he believed, for instance, that by fertilizing a species with 

 a mixture of its own and foreign pollen it would be possible to obtain a kind 

 of semi-hybrids, which would be somewhat, but not very much unlike the 

 mother species. Further, he mixed his speculations up with certain mystical 

 ideas, particularly in the sphere of alchemy; he expressly compares the change 

 that the characters of the species undergo in hybridization with the con- 



