MUTATIONS, VARIATIONS, AND RELATIONSHIPS OF THE OENOTHERAS. 23 



The branchinq habit of Oenothera ruhrinervis. — In discussing the branching 

 of Oenothera rubrinervis in 1904 the statement was made that "such a char- 

 acter as this is too largely influenced by the individual physiological vigor to 

 be of any value as a diagnostic character, " and this statement receives striking 

 confirmation in the conditions observed in 1905. The specimens of (9. rubri- 

 nervis grown at the Station for Experimental Evolution in the latter year were 

 totally different in their branching from those studied the year before at the 



22-24- 25-27 28-30 31-33 34-36 37-39 40-42 43-45 46-48 



Fig. 3. — Comparison of the number of branches of Oenothera lamarckiana (shaded with lines rising 

 toward the right) and O. ruhrinervis, as grown at the Station for Experimental Evolution in 1905. 



New York Botanical Garden. There was in 1905 almost a complete sup- 

 pression of the large basal branches which were such a marked feature of the 

 specimens earlier described. Instead of finding Oenothera lamarckiana and 

 O. rubrinervis entirely distinct and separated by a wide gap in respect to 

 number of lateral branches, the curves in figure 3 show how greatly they 

 overlap. Their numerical relations may be studied in the following table : 



