RECENT PAPERS ON (ENOTHERA MUTATIONS. 

 By R. Ruggles Gates, M.A., Ph.D. 



[^Reprinted from The New Phytologist, Vol. XII, No. 8, 

 October, 1913.'] 



SINCE the publication of De Vries's mutation theory the investi- 

 gations with (Enothera have become manifold, and have 

 included almost every phase of the subject which bears in any way 

 on genetic research. The CEnotheras have been and are still being 

 closely examined from every point of view which may throw light 

 upon their peculiar and complex behaviour. As a result of these 

 extensive investigations of the phenomena of heredity and variation, 

 as well as of the cytology, distribution, systematics and various other 

 features, the mutating (Enotheras are perhaps better known than 

 any other group of plants of corresponding size. 



The accumulated data of the last decade have added much to 

 the complexity of the facts, without, in many cases, an equivalent 

 amount of explanatory simplification. Many of the hybridization 

 results are now, however, becoming more clarified, — at least in the 

 sense that they are seen to be consistent with each other, — while the 

 cytological work has been most serviceable in furnishing an 

 explanatory basis for the mutation phenomena themselves, removing 

 some of these problems from the region of speculation to that of fact. 



The papers on (Enothera have become so numerous in recent 

 years that a complete bibliography of the subject is already a some- 

 what extensive undertaking, so I shall mention only certain of the 

 more recent papers to indicate the later results and the present 

 position of investigation in this subject. The contributions for the 

 most part group themselves as dealing with (i.) the heredity and 

 variation, (ii.) the cytology and (iii.) the systematics of the group. 

 We may therefore conveniently consider them in that order in part, 

 though the close relationship between the cytological and breeding 

 results in this genus makes it quite impossible to deal with these 

 two phases independently of each other. Indeed, the CEnotheras 

 furnish the best example we have in plants, of the manner in which 

 hybridization and microscopic study should go hand in hand in 

 attempting an explanation of hereditary phenomena. 



The breeding experiments with (Enothera have been greatly 

 extended in scope since the publication of Die Mutationstheorie by 

 De Vries, and I shall only mention a few of the papers on this 

 subject. Extensive crossing experiments have been carried on, not 

 only with (Enothera Lamarckiana and its mutants, but with various 

 races of O. biennis, 0. grandiflora, O. muricata, O. Hookeri and other 

 species. 



The earlier crosses made by De Vries among the mutating 

 forms showed a variety of types of behaviour, the peculiarities of 

 which have since been explained in part by the cytological results. 

 When such mutants as rubrinervis, nanella and lata are crossed 

 with Lamarckiana the Fj^ contains both parent types in varying 

 proportions, and in the first case both these types breed true. On 

 the other hand, when Lamarckiana is crossed with its putative 

 derivative hrevistylis the latter behaves as a simple Mendelian 



