52 MUTANTS AND HYBRIDS OF THE OENOTHERAS. 



a matter of much doubt, but field expeditions guided by descriptions 

 from Bartram's travels in 1776 resulted in a rediscovery of the species 

 in a spot not far from the original locality. This found, the confusion 

 which had arisen as to the separation of this species and 0. lamarck- 

 iana is cleared up. 



The cultures of the evening-primroses made in the New York 

 Botanical Garden show that two or more elementary species are 

 grouped under some of the specific names as ordinarily accepted. 

 The failure to recognize these elements has resulted in the prevalent 

 opinions as to the wide range of fluctuating variability exhibited by 

 these plants. This is especially true of 0. biennis , which has enjoyed 

 a reputation for variation not justifiable by systematic and orderly 

 observations made on plants grown under various conditions. One of 

 the forms, apparently typical of the true O. biennis now under culti- 

 vation, is in a mutative condition, but description of the derivatives 

 is reserved until they have completed a cycle of development. 



O. cruciata as it exists at the present time in the cultures in the 

 New York Botanical Garden, and in the Botanical Garden of Amster- 

 dam is composed of three elementary species, which are fairly distinct 

 and without intergrading forms. A careful analysis of the occurrence 

 of the group leads to the inevitable conclusion that one of the forms 

 is in a mutating condition. 



It is evident that in the investigations of native species for 

 possible mutating forms, the first and most important task to be 

 completed is that of the resolution of the forms selected into their 

 elementary constituents. Otherwise the seed obtained from plants 

 belonging to separate strains might well give an appearance of 

 variability not justifiable by the facts. Mutations, therefore, may be 

 taken as properly authenticated only when appearing in guarded 

 pedigree-cultures from seeds produced by a known individual, which 

 should be preserved for comparison. Discussions of mutants secured 

 under other conditions may serve an important purpose in offering 

 clues which will be useful in the selection of research material, but 

 can have no direct or actual value as a contribution to the subject. 



The evening-primroses of eastern North America, from which 

 probably all of the forms cultivated in Europe are derived, may be 

 divided into two groups a group including 0. biennis, muricata, 

 oakesiana, and cruciata, in which the flowers are comparatively small, 

 and in which self-pollination is possible and frequent. The second 

 group, including species native to a region farther south, comprises 0. 

 argillicola, O. grandiflora, and O. lamarckiana, in which the flowers are 

 large and the stamens are much shorter than the pistil, a condition 

 which with some accessory structures favors cross-pollination. 



