THE FL^UCTUATIONS OF OENOTHERA LAMARCKIANA AND 



ITS MUTANTS. 



By George Harrison Shull. 



The results of statistical studies made in 1904 on Oenothera lamarckiana Ser. 

 and two of its mutants, 0. nanella and O. rubrinervis, were so suggestive that 

 it was thought desirable to make a further attempt to trace the relations of 

 the mutants to their parental form, as indicated by the variations in some 

 of their differentiating characters. In order to reduce the probable error, it 

 was necassary to secure data from a larger number of individuals than the 

 cultures at the New York Botanical Garden could supply. Consequently cul- 

 tures of several of the Oenotheras were begun at the vStation for Experimental 

 Evolution. 



The cultures which form the basis of this comparative study were the 

 following: 



(a) About 90 spscimens of 0. lamarckiana were grown from seed supplied 

 under the designation D.1.8 by the senior author, being seed from plants 

 guarded and purely self-fertilized for three generations in the New York 

 Botanical Garden, and thirteen generations preceding in the Botanical Gar- 

 den at Amsterdam. In this, as in all the following cultures, no selection of 

 specimens was made, the desired number of plants having been taken consecu- 

 tively, beginning at one side of the seed-pan ; and in all cases the arrangement 

 in the garden was the same as that adopted at the New York Botanical Garden, 

 i. e., the plants were placed at a uniform distance of i meter from each other. 

 One of these 90 individuals was an O. lata and was omitted from the statistical 

 studies on this plot. The remaining 89 specimens were typical 0. lamarckiana. 



(b) Ten rosettes of Oenothera lamarckiana were received by mail from Prof. 

 De Vries April 7, 1905, having been collected by him in the open field near 

 Hilversum, Holland, where over twenty years ago he secured the original 

 stock for his pedigree-cultures; 9 of these came to bloom and were uni- 

 form in appearance, agreeing well with the other cultures of O. lamarckiana 

 in all characters but those whose differences could be appropriately attributed 

 to the fact that these plants had grown as biennials, while the others had been 

 forced to annual bloom by giving an early start in the propagating house. 

 The chief differences between these plants and those of the culture described 

 above were seen in the greater height and more numerous and longer branches 

 of the plants from Hilversum. The rosette leaves were more numerous and 

 larger in both dimensions, but had the same form and the same degree of 

 crinkling. 



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