TWIN HYBRIDS FROM CROSSES OF CENOTHERA LA- 



MARCKIANA AND FRANCISCANA WITH CE. 



PYCNOCARPA, IN THE F^ AND F,. 



(Plates I-IV.) 



By GEORGE F. ATKINSON; 



(Read April 13, 1917.) 



The peculiar behavior of Qinotlicra pycnocarpa and CE. nutans in 

 reciprocal crosses^ (Atkinson, 191 7) led me to undertake reciprocal 

 crosses of these with other species of CEnothera. Among the species 

 which were used more attention has been given to Qinotlicra la- 

 marckiana and (E. franciscana.- Seed of the former was obtained 

 from de Vries, of the latter from H. H. Bartlett. 



Reciprocal crosses of these two species with Qinothera nutans 

 gave results which indicated that twin hybrids were produced in the 

 F-L. The plants were grown as annuals in 191 5, so that the observa- 

 tions were made on summer rosettes and on the mature plants. 

 The number of individuals in some of these crosses was few. The 

 broad leaves of CE. nutans, however, resembling in general form 

 and size those of CE. lamarckiana and franciscana, made an analysis 

 of the results more difficult and uncertain than in the reciprocal 

 crosses when CE. pycnocarpa was used, since its rosette leaves are 

 narrow and deeply cut over the proximal half. 



This paper, therefore, treats only of the reciprocal crosses of 

 CE. lamarckiana and franciscana, with CE. pycnocarpa. The pollina- 

 tions for the reciprocal crosses were made during the season of 

 1914. The seeds were sown in ]\Iarch, 191 5, transplanted to flats or 

 pots in April, and then transplanted to the garden in June. The 

 season was quite rainy until the latter part of August and in Sep- 



1 These Oenothera studies were undertaken more from tlie morphological 

 standpoint than from that of plant hreeding. 



2 CEnothera franciscana Bartlett, Rhodora, 16, 35, 1914. This species, like 

 CE. lamarckiana, is one of the large-flowered, open pollinated species. 



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