KNOWLEDGE OF THE MUTATING OENOTllEEAS. 15 



pi. 1534.) They are also found in various other parts of England, and are widely 

 distributed, particularly on sand-dunes and along railway -lines in France, Germany, 

 Holland, and in fact all over Europe. They also occur in such regions as the Azores, 

 South Africa, Australia, Japan, &c., and I have obtained new races with unexpected 

 characters in cultures of seeds from some of these localities. The origin of such races is 

 a problem of much interest, and may furnish important data on the question of the 

 effects of climate in the origin of races. It is very desirable that detailed studies of 

 naturalized colonies of Oenotheras in various parts of the world should be undertaken. 



I 



S;pecijic Differences. — The species with which the students of the mutating Oenotheras 

 have been chiefly concerned are O. Lamarclciana^ O. grandijlora^ 0. biennis, and 

 O. muricata. An analytical key (Gates, 1909 c) gives the main distinguishing features 

 of these species and their segregates and relatives, and subsequent papers (Gates, 

 1911 «, 1911 d) have traced the history of the origin of these names as they were 

 applied to races introduced into European Gardens. It seems desirable to point 

 out that after long familiarity with these forms I find it necessary to conclude 



a- 



that the limits between the species are purely arbitrary. Eixed limits can only be 

 maintained as a matter of convenience in dealing with a host of forms. Eor races are 

 found which overstep any boundary-line which can be drawn between each species and 

 those to which it is most closely related. The type of each species is only ooe of many 

 related races which have come to be included with the type in systematic descriptions. 

 Which of these races originally received the name of a given species was purely a matter 

 of chance, because it was the first to come under the botanist's notice. But while these 

 types furnish useful landmarks, yet, when whole series of additional races are observed, 

 they must either be given new specific names or classed as races under certain species 

 already described. The advisability of giving specific rather than racial names to these 

 newer-discovered forms will not be discussed here, but it is sufficiently clear that names 

 of some sort are necessary in dealing with them, either from the standpoint of a more 



complete knowledge of the flora of any country, or from that of the evolutionary 



experimentalist who must have names to designate the various forms with which he 

 works. "When these forms diff'er in sinsrle characters, such as flower-colour, which can 

 be described in one word, that word is all that is necessary for a name. But when such 

 geographic races differ slightly in many characters afi'ecting leaf, stem, flower, and fruit, 

 as in Oenothera, the necessity for an accurate description and a name for each such race 

 is sufiaciently evident, and is highly desirable both from the systematic and the breeding 



point of view. 



Since, therefore, more or less arbitrary lines of distinction between the species are 

 necessary I have, for convenience, adopted the following : — 0. Lamarckiana and 

 O. grandifiora forms nearly agree in flower-size, but the latter have no long muricated 

 hairs, or very few, on their sepals, while the former possess at least a considerable 

 number. The O. grandiflora races are also characterized by possessing rosette-leaves 

 with deep basal lobes, while these do not occur in the known O. LamarcMana races. 

 The 0. biennis races differ from the two previous groups only in having smaller flowers 



