CHAP, i.] Karl Fricdrich Gartner. 429 



the co-operation of the pollen is indispensable to the formation 

 of the embryo in the growing seed, and that plants therefore 

 have sexuality exactly as animals have it. Gartner did not 

 content himself with simply making new experiments in fertili- 

 sation ; he refuted the objections of Spallanzani, Schelver, 

 Henschel, Girou and others in detail from fresh experiments 

 and from other sources of information, paying particular regard 

 to all the circumstances which could come under consideration 

 in each case ; he exposed the inaccuracy of the observations of 

 the opponents of sexuality point by point, and finally called at- 

 tention to a number of remarkable phenomena observable in the 

 ovary even before fertilisation, and to the circumstances under 

 which the pollen may find its way to it in cases where ordinary 

 pollination has been apparently prevented. These observations 

 once more confirmed the existence of sexuality in plants, and 

 in such a manner that it could never be again disputed. 

 When facts were observed in 1860, which led to the pre- 

 sumption that under certain circumstances in certain indi- 

 viduals of some species of plants the female organs might 

 produce embryos capable of development without the help of 

 the male, there was no thought of using these cases of 

 parthenogenesis to disprove the existence of sexuality as the 

 general rule ; men were concerned only to verify first of all 

 the occurrence of the phenomena, and then to see how they 

 were to be reasonably understood side by side with the 

 existing sexuality, as had to be done also in the corresponding 

 cases in the animal kingdom. 



Gartner's work on hybridisation had been preceded by other 

 enquiries into the same subject, those namely of Knight men- 

 tioned above at the beginning of the century, and Herbert's 

 more ample investigations published in his work on Amaryl- 

 lideae in 1837. Gartner did not neglect to compare his 

 observations at all points with the results of his predecessors, 

 especially those of Koelreuter, and he deduced from the 

 astonishing mass of material a number of general propositions 



