witli Hieracium 99 



an exact knowledge of the structure and fertility of the 

 hybrids and the condition of their offspring through several 

 generations no one can undertake to determine the possible 

 influence exercised by hybridisation over the multiplicity 

 of intermediate forms in Hieracium. The condition of 

 the Hieracium hybrids in the range we are concerned with 

 must necessarily be determined by experiments ; for we do 

 not possess a complete theory of hybridisation, and we may 

 be led into erroneous conclusions if we take rules deduced 

 from observation of certain other hybrids to be Laws of 

 hybridisation, and try to apply them to Hieracium without 

 further consideration. If by the experimental method we 

 can obtain a sufficient insight into the phenomenon of 

 hybridisation in Hieracium, then by the help of the ex- 

 perience which has been collected respecting the structural 

 relations of the wild forms, a satisfactory judgment in 

 regard to this question may become possible. 



Thus we may express the object which was sought after 

 in these experiments. I venture now to relate the very 

 slight results which I have as yet obtained with reference 

 to this object. 



1. Respecting the structure of the hybrids, we have 

 to record the striking phenomenon that the forms hitherto 

 obtained by similar fertilisation are not identical. The 

 hybrids H. prcealtum 9 x ff. aurantiacum $ and H. Auri- 

 cula ? x H. aurantiacum $ are each represented by two, 

 and H. Auricula ^ x ff. pratense <$ by three individuals, 

 while as to the remainder only one of each has been 

 obtained. 



If we compare the individual characters of the hybrids 

 with the corresponding characters of the two parent types, 

 we find that they sometimes present intermediate structures, 



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