408 History of the Sexual Theory. [BOOK in. 



many less gifted observers in the course of many years. But 

 the same thing happened now, which happens often in similar 

 cases and which happened to Camerarius ; a much longer time 

 elapsed before others learnt to understand the meaning and 

 importance of Koelreuter's labours, than he had found necessary 

 for making his discoveries. 



Koelreuter's most important and best-known work appeared 

 in four portions in 1761, 1763, 1764 and 1766 under the title, 

 ' Vorlaufige Nachricht von einigen das Geschlecht der Pflanzen 

 betreffenden Versuchen und Beobachtungen ' ; we shall en- 

 deavour to give a brief summary of the more important 

 results. 



At different places in this work occur remarks and experi- 

 ments on arrangements for pollination, which up to that time 

 had been seldom and only hastily observed. As the pollen- 

 tube had not yet been discovered, and Koelreuter himself set 

 out with the view, that a fluid finds its way from the pollen- 

 grains as they lie on the stigma to the ovules, it was important 

 first of all to determine the quantity of pollen which is required 

 for the complete fertilisation of an ovary ; with this object 

 in view Koelreuter counted the pollen-grains formed in a 

 particular flower and compared them with the number required 

 to be applied to the stigma in order to effect complete 

 fertilisation, and he found that the latter number was much 

 the smaller. For instance, he counted four thousand eight 

 hundred and sixty-three pollen-grains in a flower of Hibiscus 

 venetianus, while from fifty to sixty were sufficient to produce 

 more than thirty fertile seeds in the ovary ; in Mirabilis jalapa 

 and Mirabilis longiflora he counted about three hundred grains 

 of pollen in the anthers, while from two to three or even one 

 sufficed for fertilisation in the one-ovuled ovary. He also tried, 

 whether in flowers with divided and even deeply-cleft styles 

 fertilisation could be effected in all compartments of the ovary 

 through one of them only, and he found that it could. 



Koelreuter directed special attention to the arrangements, 



