290 
R. Ruggles Gates. 
RECENT PAPERS ON (ENOTHERA MUTATIONS. 
By R. Ruggles Gates, M.A., Ph.D. 
Q INCE the publication of De Vries’s mutation theory the investi- 
IO gations with CEnothera 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 CEnotheras 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 CEnothera 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 CEnothera have been greatly 
extended in scope since the publication of Die Mntationstheorie 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 CEnothera Lamarckiana and its mutants, but with various 
races of 0. biennis, 0 . grandijiora , 0. mnricata, 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 P x 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 brevistylis the latter behaves as a simple Mendelian 
