Oenothera Riibrinervis. 333 



Fig. 68 with the similar ones of O. Lamarckiana Figs. 

 64-66). 



The narrow form of the leaves is well brought out 

 in Figs. 52 and 54. The older the plants become the 

 greater becomes the difference and the more certain the 

 diagnosis. As a rule I have removed the mutants at an 

 age when they have about twice as many leaves as the 

 rosette figured at Fig. 68 C. The plants shown there 

 are, of course, not mutants but are raised from seeds 

 of 0. ruhrinervis and selected from the crop as the most 

 typical examples of that species. 



As the plants get older the veins of the leaves lose 

 their pale red color more or less ; but this depends on 

 how they are grown and on the amount of sun they 

 get. On the other hand, with age the red pigment be- 

 comes more evident in the inflorescences, the flowers and 

 the unripe fruits, thereby contributing greatly to the 

 characteristic look of the species. The young internodes 

 of the stem are suffused with red, and this color is par- 

 ticularly pronounced in the swollen bases of the larger 

 hairs. The tips of the calyx are spotted with red and the 

 flowers become much darker when they wither than those 

 of O. Lamarckiana, reminding one of those species the 

 leaves of which become red when they wither, such as 

 O. stricta, 0. missouriensis, and particularly the white 

 O. acanlis. The fruits are marked with four broad, 

 dark red, longitudinal stripes, one along the middle of 

 each valve. But in this case the redness varies accord- 

 ing to the position of the fruits and from individual to 

 individual within apparently wide limits; sometimes, in- 

 deed, the stripes are very difficult to find. 



This red pigment occurs also in 0. Lamarckiana and 

 particularly in the unripe fruits ; but very indistinctly : 



