introductory remarks ^ 



Experience of artificial fertilisa- 

 tion, such as is effected with orna- 

 mental plants in order to obtain new 

 variations in colour, has led to the ex- 

 periments which will here be discussed. 

 The striking regularity with which the 

 same hybrid forms always reappeared 

 whenever fertilisation took place be- 

 tween the same species induced further 

 experiments to be undertaken, the ob- 

 ject of which was to follow up the 

 developments of the hybrids in their 

 progeny. 



To this object numerous careful ob- 

 servers, such as Kolreuter, Gartner, 

 Herbert, Lecoq, Wichura and others, 

 have devoted a part of their lives with 

 inexhaustible perseverance. Gartner 

 especially, in his work "Die Bastarder- 

 zeugung im Pflanzenreiche" (The Pro- 

 duction of Hybrids in the Vegetable 

 Kingdom), has recorded very valu- 

 able observations; and quite recently 

 Wichura published the results of some 

 profound investigations into the hy- 

 brids 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 ex- 

 periments made on plants belonging to 

 the most diverse orders. 



Those who survey the work in this 

 department will arrive at the convic- 



1 This translation was made by the Royal 

 Horticultural Society of London, and is re- 

 printed, by permission of the Council of the 

 Society, with footnotes added and minor 

 changes suggested by Professor W. Bateson, 

 enclosed within I 1. The original paper was 

 published in the Verb, vatiirf. Ver. in Brmm, 

 Abhandlungen, iv. 1865, which appeared in 

 1866. 



MENDEL 



tion that among all the numerous ex- 

 periments 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 definitely 

 to ascertain their statistical relations.^ 



It requires indeed some courage to 

 undertake a labour of such far-reach- 

 ing extent; this appears, however, to 

 be the only right way by which we 

 can finally reach the solution of a 

 question the importance of which can- 

 not be overestimated in connection 

 with the history of the evolution of 

 organic forms. 



The paper now presented records 

 the results of such a detailed experi- 

 ment. This experiment was practically 

 confined to a small plant group, and 

 is now, after eight years' pursuit, con- 

 cluded in all essentials. WTiether the 

 plan upon which the separate experi- 

 ments were conducted and carried out 

 was the best suited to attain the de- 

 sired end is left to the friendly decision 

 of the reader. 



SELECTION OF THE EXPERIMENTAL 

 PLANTS 



The value and utility of any experi- 

 ment are determined by the fitness of 

 the material to the purpose for which 

 it is used, and thus in the case before 

 us it cannot be immaterial what plants 

 are subjected to experiment and in 

 what manner such experiments are 

 conducted. 



The selection of the plant group 

 which shall serve for experiments of 

 this kind must be made with all pos- 



2 [It is to the clear conception of these 

 three primary necessities that the whole suc- 

 cess of Mendel's work is due. So far as I 

 know this conception was absolutely new in 

 his day.] 



