MUTATIONS, VARIATIONS. AND RELATIONSHIPS OF THE OENOTHERAS. 9 



in 1S37, and at other places since then, forming now quite a feature of the 

 Liverpool sandhills, which has been shown by our cultures to be the lamarck- 

 iana around which so much interest clusters. It would seem difficult in the 

 light of these facts to find any basis upon which the conclusion that this plant 

 had been derived from 0. grandiflora might rest. 



The plant originally introduced into Europe under the name of O. biennis 

 seems to have been a large-flowered form altogether different from the plant 

 under that name as known in America. Then (K lamarckiana grown from 

 imported seeds or their progeny, and O. grandiflora from Alabama, present 

 a verv different aspect and have but little resemblance to the O. biennis of 

 the waste lands of eastern America. 



THE MUTABILITY OF OENOTHER.A L.4M.ARCKIANA. 



About 2500 plantlets of O. lamarckiana derived from various sources have 

 been brought under observation, as described above. Of these 106 or a little 

 over 4 per cent were mutants. One culture (C.1.2) appeared to give a much 

 higher proportion of mutants, but a failure to make a record of one lot of 

 discarded plants makes it impossible to confirm this. The behavior of this 

 lot of plants and also the confusion of fasciated specimens of O. lamarckiana, 

 in the rosette stage, with mutants, led the senior author to assert that the pro- 

 portion of mutant derivatives in pedigreed cultures of O. lamarckiana had 

 been increased from 5 to 6 per cent of the progeny (MacDougal, 1905). 

 In no culture of later date has it been possible to exceed the maximum propor- 

 tion of 5 per cent, and the greater majority fall much below this figure. While 

 the coefficient of mutabilitv has not been modified vet, one or two forms have 

 appeared which were not recognizable in a rosette stage by Professor De 

 Vries, and probably constitute an extension of the range of mutability. This, 

 however, may not be interpreted to mean an efl'ect of local conditions. All 

 of the mutants now known did not occur in the cultures in Amsterdam 

 during the first few years of the cultures. ]\Iany, in fact, occur so rarelv 

 that by the law of probability it is necessary to grow many thousands of speci- 

 mens in order to secure one individual of the rare type. In accordance with 

 this same principle it is to be seen that the spreading of the cultures of O. 

 lamarckiana may be expected to bring to light other rarer derivatives. When 

 such forms are found it is not to be interpreted as a result of local conditions 

 of the culture in which they appear, but simply in accordance with the coeffi- 

 cient of mutabihty of the parental type with respect to the form in question. 



The uniformly low frequency of mutants in material procured from seeds- 

 men is a matter not altogether understood. Among the probabilities to be 

 taken into account is that the seeds mav have lain in storage for more than 

 one season before being planted, in consequence of which the unequal hardi- 

 ness of the mutants and the parent might operate to decrease the apparent 



