174 BOTANICAL GAZETTE [march 



•contradiction with the other hypotheses. If we accept these views, 

 all reasons for supposing a correlation between the splitting phe- 

 nomenon and the mutabiHty would lose their value, and this 

 latter process would come much nearer to the corresponding 

 changes in 0. biennis and allied species. The hypothesis, although 

 resting on too large a number of suppositions, would in some sense 

 be a support for the theory of mutation, since it is evidently impos- 

 sible that these presumed qualities, which are incompatible with 

 life, could have evolved slowly on the ground of their utility in the 

 struggle for existence. Moreover, the hypothesis has no direct 

 bearing on the observed phenomena of mutation, and the fact that 

 in O. biennis such empty seeds are wholly or almost wholly absent 

 proves beyond doubt that mutability may be independent of 

 them. Thus the hypothesis of Renner emphasizes the importance 

 of a study of the mutation phenomena in 0. biennis, in contra- 

 distinction to those in 0. Lantarckiana, at least for the present, 

 until facts are available to appreciate the correctness of his views. 



Obviously the hypothesis that 0. Lamarckiana might be a 

 hybrid, whilst 0. biennis is not, can in no way account for the 

 phenomena of mutation which are common to both of these species. 

 For this reason it seems important to describe the degree of muta- 

 bility as it has been observed, up to this time, in O. biennis, which 

 is, next to 0. Lamarckiana, the most suitable species for this kind 

 of research. The mutations in the other forms seem to be far 

 more rare, and therefore require many more thousands of indi- 

 viduals for a statistical study or for experiments upon their causes. 



Besides the assumption that 0. Lamarckiana might be a hybrid, 

 some authors have recently pointed out that hybridism may be one 

 of the chief ways in which species are produced in nature, especially 

 in the larger or so called polymorphous genera. Linnaeus was 

 the first to propose this hypothesis, at the time when the number of 

 discovered forms was growing so fast as to make it almost impossible 

 to assume a separate creation for every one of them. I have not 

 the least doubt that Linnaeus and his followers were right in this 

 point, and that many wild species have been produced by the 

 sexual combination of the characters of their aUies. How great 

 a r61e this kind of hybridization or of the recombination of char- 



