with Hieracium 367 



not become fertilised by their own pollen in the ordinary 

 course of self-fertilisation. 



It not rarely happens that in fully fertile species in the 

 wild state the formation of the pollen fails, and in many 

 anthers not a single good grain is developed. If in these 

 cases seeds are nevertheless formed, such fertilisation must 

 have been effected by foreign pollen. In this way hybrids 

 may easily arise by reason of the fact that many forms 

 of insects, notably the industrial Hymenoptera, visit the 

 flowers of Hieracia with great zeal and are responsible for 

 the pollen which easily sticks to their hairy bodies reaching 

 the stigmas of neighbouring plants. 



From the few facts that I am able to contribute it 

 will be evident the work scarcely extends beyond its first 

 inception. I must express some scruple in describing in 

 this place an account of experiments just begun. But the 

 conviction that the prosecution of the proposed experiments 

 will demand a whole series of years, and the uncertainty 

 whether it will be granted to me to bring the same to a 

 conclusion have determined me to make the present com- 

 munication. By the kindness of Dr Nageli, the Munich 

 Director, who was good enough to send me species which 

 were wanting, especially from the Alps, I am in a position 

 to include a larger number of forms in my experiments. 

 I venture to hope even next year to be able to contribute 

 something more by way of extension and confirmation of 

 the present account. 



If finally we compare the described result, still very 

 uncertain, with those obtained by crosses made between 

 forms of Pisum, which I had the honour of communicating 

 in the year 1865, we find a very real distinction. In Pisum 

 the hybrids, obtained from the immediate crossing of two 

 forms, have in all cases the same type, but their posterity, 

 on the contrary, are variable and follow a definite law in 

 their variations. In Hieracium according to the present 

 experiments the exactly opposite phenomenon seems to be 

 exhibited. Already in describing the Pisum experiments 

 it was remarked that there are also hybrids whose posterity 

 do not vary, and that, for example, according to Wichura 

 the hybrids of Salix reproduce themselves like pure species. 

 In Hieracium we may take it we have a similar case. 



