62 MUTATIONS, VARIATIONS, AN'D RELATIONSHIPS OF THE OENOTHERAS. 



A number of radium pencils were taken from a series used by Dr. Gager in 

 his investigations, and were fastened in an inflorescence in such manner that a 

 deleterious influence must have been exerted on some ovules, while in other 

 cases the effect must have been stimulative if the reactions of seedlings of 

 other plants may be taken to offer a fair analogy. The crop of seeds matured 

 in the treated ovaries was sown in September, 1905, and late in November a 

 census showed that only 20 normal specimens of laniarckiana were present 

 and that 2 mutants were also included. The rate of mortality was thus seen 

 to be twice as great in the type as in the mutants in this single test. 



Similar tests were made with 0. biennis. Solutions of magnesium sulphate 

 in distilled water were used without any noticeable departure in the composi- 

 tion or behavior of the progeny arising from the seeds. Poisonous solutions 

 containing i part of zinc sulphate in 500 of distilled water were also used. 

 The seeds produced in the ovaries which had received this treatment contained 

 atypic forms of the kind seen in ordinary cultures in apparently the cus- 

 tomary proportion of about one in 200. In addition however, a single rosette 

 was found which differed widely from any known type, and of this form, which 

 was recognizably different from the parental type in many qualities, some of 

 the differences were plainly apparent even in the earliest leaves of the seedlings. 

 These differences have become accentuated in the adult plant. 



The parental form has been under observation for five years in cultures 

 and in a wild condition. An aberrant form, which appears to be eversporting, 

 has been previously figured, and while this form appeared in the injected 

 or treated seeds in a normal proportion, yet the newest aberrant has not been 

 seen elsewhere. The probability must be taken into account that it may be 

 a mutant of rare occurrence, the cycle of which came within the experiments ; 

 but in either case it is plainly a mutant, and it only remains to be seen whether 

 or not it was induced by the action of the zinc solution. The presumption 

 seems to favor such a conclusion. Seeds of this form were harvested in 

 August, 1906, and sown immediately, with the result that the characters of 

 the new form were found to be fully transmissible, the first generation of the 

 progeny being duplicates of the parent within the limits of fluctuating varia- 

 bility. The entire plant is characterized by a much deeper green color than 

 the parental form and the leaves are slightly curled and twisted, owing to 

 inequalities of growth, and it reaches maturity quite early in the season. 



In addition to the crop of guarded seeds harvested from some of the 

 branches, the available remainder were collected and sown in the greenhouse of 

 the Dessrt Laboratory, with the result that this second generation of the deriv- 

 ative was found to conform exactly in every individual to the derivative type. 

 Either the mutant does not intercross with the parent, although the branches 

 were in contact, or if a cross has occurred the derivative qualities are dominant. 

 This matter may be determined by the time this paper finds its way through 



