Mendel's Experiments in Hybridisation 41 



of the Willow. That, so far, no generally applicable law 

 governing the formation and development of hybrids has 

 been successfully formulated can hardly be wondered at by 

 anyone who is acquainted with the extent of the task, and 

 can appreciate the difficulties with which experiments of 

 this class have to contend. A final decision can only be 

 arrived at when we shall have before us the results of 

 detailed experiments made on plants belonging to the most 

 diverse orders. 



Those who survey the work done in this department 

 will arrive at the conviction that among all the numerous 

 experiments made, not one has been carried out to such an 

 extent and in such a way as to make it possible to determine 

 the number, of different forms under which the offspring of 

 hybrids appear, or to arrange these forms with certainty 

 according to their separate generations, or to definitely 

 ascertain their statistical relations*. 



It requires indeed some courage to undertake a labour 

 of such far-reaching extent ; it appears, however, to be the 

 only right way by which we can finally reach the solution 

 of a question the importance of which cannot be over- 

 estimated in connection with the history of the evolution 

 of organic forms. 



The paper now presented records the results of such 

 a detailed experiment. This experiment was practically 

 confined to a small plant group, and is now, after eight 

 years' pursuit, concluded in all essentials. Whether the 

 plan upon which the separate experiments were conducted 

 and carried out was the best suited to attain the desired 

 end is left to the friendly decision of the reader. 



' [It is to the clear conception of these three primary necessities 

 that the whole success of Mendel's work is due. So far as I know 

 this conception was absolutely new in his day.] 



