20 MUTATIONS, VARIATIONS, AND RELATIONSHIPS OF THE OENOTHERAS. 



species; 15 were 0. lamarckiana, and 2 were O. nanella. The remaining 10 

 were not positively identified, though several which were at first thought to 

 be O. lata but which were afterwards seen to differ from that species in certain 

 bud characters, especially in the possession of pollen-bearing anthers, may 

 have been true hybrids between 0. lata and O. gigas. 



The advantages of bringing together to one place for use in this line of 

 investigation material having such different past histories will be obvious. If 

 the various types of structure which have been separated and described under 

 specific names are not perfectly natural centers of stability, or rather of equi- 

 libration, but are the product of selection, it is inconceivable that the forms 

 resulting from selection by different persons for different periods of time and in 

 different environments should produce identical forms, and especially that 

 there should be identity in characters that were not taken into account and 

 could not well be taken into account by those making the selections. 



Some differences are naturally to be expected in the characters of these 

 several lots of plants of the same species coming from different sources, 

 because of the known behavior of purely fluctuating characters, and the degree 

 of these differences will be contemplated with some interest. On the other 

 hand, the various sources of the material will make the comparisons between 

 the different species less satisfactory than might be wished. 



A part of the advantage gained in the way of larger quantities of material 

 by bringing these cultures to the Station for Experimental Evolution is offset 

 by the fact that differences in soil, climate, and methods of culture from those 

 to which the cultures were subjected at the New York Botanical Garden in 

 1904 will make impossible the drawing of any conclusions this year regarding 

 the problem which originally incited these investigations, namely, the question 

 as to the presence or absence of regression in the mutants. As a partial 

 measure of the difference in conditions at the New York Botanical Garden in 

 1904 and at the Station for Experimental Evolution in 1905, a comparison of 

 the heights of the 0. lamarckiana used for the studies in the former year may 

 be made with those of the first lot (a) described on page 1 8. Both of these lots 

 were raised as annuals and should therefore give a reasonably fair indication 

 of the relative value of the resultant of all the factors affecting the fluctuating 

 characters of the two lots of plants. 



The height-curves reduced to equal areas are shown superposed in fig. i, 

 and the principal constants are as follows : 



