SOME SEGREGATES OF OENOTHERA. 125 



The following key is prepared largely from the characters 

 of the plants as they have appeared in my own cultures. 

 The only exceptions are 0. argillicola, the account of which 

 is taken from MacDougal, Carnegie Pub. 24: 11. pL 7. 1905, 

 and Mackenzie, Notes on evening primroses, (Torreya, 4= : 

 56-57), 1904; 0. Simsiana, 0. Oakesiana, 0. muricata and 

 0. parvifiora, the account of which is from Vail, Carnegie 

 Pub. 81. 1907; and 0. elliptica,0. suhlimaris, and 0. scintiU 

 lans, which I have not grown, and for which the description 

 has been taken from DeVries' account. DeVrics, in his 

 Mutationstheorie, 2 : 322-328, has already prepared several 

 keys to the mutants, based respectively on seedhng 

 characters; height and branching of plants; leaves; and 

 flowers, fruits and seeds. In the following key, characters 

 are chosen from all the stages of development, and, as far as 

 possible, from those which are most Ukelyto be encountered 

 by a botanist in the field. The selection of differentiating 

 characters under these circumstances is a difficult one and 

 I am not sure that the choice I have made is always the 

 best. But short descriptions, enumerating the chief dis- 

 tinctive features of the various forms, are appended for 

 aid in case the stages chosen in the keys are not available, 

 or the distinctions drawn are not sufficiently clear. Refer- 

 ences are also given to some of the most accurate figures of 

 the different species. 



It should be said that in the case of the mutants from 

 0. Lamarckiana, occasional specimens appear which trans- 

 gress in one or more characters any hne which can be 

 drawn between related forms. Usually, however, the forms 

 fit very well the descriptions given them. 



There is no attempt to cite the extensive literature of the 

 genus here. A systematic treatment was published by 

 Small* in 1896, and a monograph by L^veillef in 1902 and 

 1905. 



* Small, John K Oenothera and its segregates. (Bull. Terr. Bot. Club. 

 23: 167-194). 1896. 



t Leveille, H. Monographic du genre Onothera. Le Mans. 1902 and 

 1905. 



