98 Mendel's Experiments 



the close attention of the experts. Regarding no other 

 genus has so much been written or have so many and such 

 fierce controversies arisen, without as yet coming to a 

 definite conclusion. It is obvious that no general under- 

 standing can be arrived at, so long as the value and 

 significance of the intermediate and transitional forms is 

 unknown. 



Regarding the question whether and to what extent 

 hybridisation plays a part in the production of this wealth 

 of forms, we find very various and conflicting views held 

 by leading botanists. While some of them maintain that 

 this phenomenon has a far-reaching influence, others, for 

 example, Fries, will have nothing to do with hybrids in 

 Hieracia. Others take up an intermediate position; and 

 while granting that hybrids are not rarely formed between 

 the species in a wild state, still maintain that no great 

 importance is to be attached to the fact, on the ground 

 that they are only of short duration. The [suggested] 

 causes of this are partly their restricted fertility or complete 

 sterility ; partly also the knowledge, obtained by experiment, 

 that in hybrids self-fertilisation is always prevented if 

 pollen of one of the parent-forms reaches the stigma. On 

 these grounds it is regarded as inconceivable that Hieracium 

 hybrids can constitute and maintain themselves as fully 

 fertile and constant forms when growing near their pro- 

 genitors. 



The question of the origin of the numerous and constant 

 intermediate forms has recently acquired.no small interest 

 since a famous Hieracium specialist has, in the spirit of 

 the Darwinian teaching, defended the view that these 

 forms are to be regarded as [arising] from the trans- 

 mutation of lost or still existing species. 



From the nature of the subject it is clear that without 



