u 



DR. E. R. GATES— CONTEIBtJTION TO A 



this locality produced O. Lamarchiana and several of its mutants, including 0. lata, 



O. ruhrinervis, O. ohlonga, and O. alUcla. My cultures from near Birkenhead have 



shown that 0. grandifiora is an equally conspicuous member of the Oenothera population 



of that locaKty. O. grandiflora and O. Lamarchiana have also intercrossed freely, 



producing a complex of forms which I have since succeeded in part in analyzing. The 



latter frequently display characters, particularly of the leaves, which are entirely different 



from anything known in O. Lamarchiana or its mutants, though the hud and flower 



characters usually correspond with O. Lamarchiana (as do the mutants of DeYries) or 



are intermediate between 0. Lamarchiana and O. grandijlora. This fact provided the 



first clue to the relationships of these aberrant types. I have isolated a number of these 



types, which are now being grown in the second or third generation. They will be 



described at a later time. These cultures are, therefore, an attempted analysis of a 



typical interbreeding colony of forms. It is hoped that naturalized or indigenous colonies 



of Oenotheras in other parts of the world will be subjected to a similar analysis, for it is 



by this means that any fall knowledge of the factors at work in the evolution 

 of the genus can be gained, I shall be grateful for seeds sent to me from any locality. 



The question which must be asked regarding the Lancashire Oenotheras is, Are all 

 these new aberrant races tbe direct result of hybrid combinations, or must an additional 

 factor of mutation be invoked to account for the origin of some of them ? We have 

 already seen that, in the case of the mutants from 0. Lamarchiana^ such a factor must 

 be invoked, for the origin of certain of the mutant characters cannot be explained on 

 the basis of bybrid splitting. In the case of the Lancashire Oenotheras, it is evident 

 that many of the new races at least are complex hybrids, even although they breed true. 

 Whether any of them have had a different origin, remains to be seen. In any case, the 

 mutational process (using the term in contradistinction to hybrid splitting) is probably 

 a result of the germinal disturbimce which the race has experienced through previous 

 crossing. On this view, mutation and hybridization are closely related processes, the 

 former being an indirect result of the latter. This does not exclude the possibility, 

 indeed probability, that mutational transformations may result also from environmental 

 action on the organism, or from other causes. 



We may now consider some of the results of an experimental analysis of these forms 

 an analysis which is not jet completed, but certain results of which need to be stated. 

 It will be remembered that these forms are in part derivatives from 0. Lamarchiana 

 and in part complex hybrids between 0. Lamarchiana and 0. grandiflora races. It is 

 possible that O. biennis may also have entered into their composition, though I have no 

 direct evidence of this. 



My first culture of these forms consisted of 56 pla 



o 



tropical hothouse 



(see Gates, 1912), Half of these developed the characteristic 0. gixmdiflora rosette (sec 

 PI. 4. fig. 47), while the remainder displayed a large number of curious rosette types 

 scarcely two being alike, but all fallinst in the series of O. LamarcMana and its mutants 



clearly rather widely divergent from O. grandiflora. The rosettes developed their 

 characters to the fullest extent, and seven of these (PL 5. figs. 59-65) are selected to 



