GENE TIC AL STUDIES ON OENOTHERA. I 



Notes on the Behavior of Certain Hybrids of 

 CEnothera in the First Generation 



BRADLEY MOORE DAVIS 



The following account is a report on the behavior in 

 the first generation of the following sets of hybrids of 

 CEnothera grown in the Harvard botanic garden in the 

 summer of 1909: (1) gigas X Lamarckiana, (2) muri- 

 cataX gigas, (3) muricata X gran (Ufl ora, (4) biennis X 

 grandiflora, (5) grandiflora X biennis. The hybrids were 

 not grown on an extensive scale, but represented rather a 

 selection from the seedlings of the best plants in order to 

 obtain for a special purpose the most vigorous crosses 

 possible. The cross pollination was made in the writer's 

 garden at Woods Hole in 1908, and the hybrids started 

 in the hothouses at Cambridge early in January, 1909. 

 Large rosettes were in most cases developed by the last 

 of May, when the selected plants were set out in the 

 botanic garden. All of the hybrids matured during the 

 summer except a few plants of the cross gigas X La- 

 marckiana, which persisted in the rosette condition. 



1. gigas x Lamarckiana. The parent forms of this 

 cross were grown from seeds of De Vries, Lamarckiana 

 having 14 chromosomes and gigas showing from a pre- 

 liminary examination apparently twice this number. 

 Twelve rosettes were planted exhibiting wide variation 

 in the forms of the leaves, eight being similar to Lamarck- 

 iana and four similar to gigas. Two of the Lamarckiana- 

 like rosettes and three of the gigas-like remained as 

 rosettes throughout the summer, the former at the end of 

 the summer being .">.,") 'A.7 dm. broad with leaves narrower 

 than those of gigas, lanceolate and narrowly spatulate 

 in form, the gigas-Yike being 4.5-5 dm. broad and indis- 

 tinguishable from those of gigas. 



Seven of the rosettes developed into mature plants 

 which were similar to one another, 1-1.1 m. high with 

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