KNOWLEDGE 0¥ THE MUTATING OENOTHERAS. 9 



determine how ihe se^re^ational type of behaviour is related to blended inheritance, 



and what features the two Iiave in common 



As regards the laws of Yariability, we have been enabled to draw a sharp distmction 

 between heritable and non-heritable variations, although, since character-changes bavin 





same external appearance may belong in cither category, we cannot safely predict 



behaviour of a variation will be in any case until it is experimentally 



^ 



what the 



tested. Notwithstanding the attention which has been focussed on discontmuous 

 variations or mutations in recent years, particularly by the work of DeVries, even those 

 which are evidently due to the simple loss of characters are still largely beyond the 

 range of our explanation. But it may reasonably be hoped that with further knowledge 

 of their origin and causes they may be brought, at least to a limited extent, under 

 experimental control. Any further advances in this direction will be of great theoretical 

 as well as practical value. 



These investigations with Oenothera have been carried out at the University of Chicago, 

 the Marine Biological Laboratory, Woods Hole, xMass., and the Missouri Botanical Garden, 

 a^hey were continued last year at the John Innes Horticultural Institution, Merton, 

 Surrey. To the Directors of all these institutions I am very greatly indebted, for the 

 facilities afforded for carrying on my cultures, and keeping photographic and other 



I am also indebted to the Carnegie Institution for a grant in aid of expenses 



ds 



1908. I have further to thank Professor Parmer for 



DO 



the preparation of this paper, and a Grant from the Eoyal Society has defrayed the 

 expenses of publishing the plates. Numerous botanists from many parts of the world 

 have very kindly sent me seeds of Oenothera species, and I shall be most grateful to 

 any botanists who will send me further seeds of wild or naturalized species from any 

 country. The study of naturalized colonies of Oenothera will furnish an important part 



of the data required. .• -. 



In connection with these cultures, as the variety of races under observation has 

 multiplied, and the number of new forms recognized has increased, the difficulties in 

 connection with the adoption of a method of nomenclature which would be serviceable 

 to experimental evolutionists and at the same time acceptable to systematists have 

 become increasingly pressing. After much thought and discussion on the subject, and 

 consultation with Dr. O. Stapf, P.Il.S., Keeper Koyal Herbarium, Kew, and Dr. A. 

 B Rendle P U.S., British Museum (Natural History), I venture to suggest the 



follo\\.^j3 ^^^o 



m 



The names of forms which are (1) known only in cultures, or (2) which have originated 

 cultivation or (3) the description of the behaviour of which is based on material long 

 cultivation, shaU be followed by the abbreviation culL, to distinguish them from forms 



derived directlv from wild 



This usage is already followed partly by systematists, and may perhaps be adopted 

 with advantage by breeders. Like every rule, however, there wiU be plenty of 



SECOND SERIES.— BOTANY, VOL. VIII. 



C 



