314 THE THEORIES OF EVOLUTION 



vis, O. oblonga and O. albida, which immediately be- 

 came constant and transmitted all their characters to 

 their offspring. 



"The giant evening-primrose, though not taller in 

 stature than O. lamarckiana, deserves its name be- 

 cause it is so much stouter in all respects. The stems 

 are robust, often with twice the diameter of lamarck- 

 iana throughout. The internodes are shorter, and the 

 leaves more numerous, covering the stems with a 

 denser foliage. This shortness of the internodes ex- 

 tends itself to the spike, and for this reason the flow- 

 ers and fruits grow closer together than on the parent- 

 plant. The fruits attain only half the normal size, 

 but are broader and contain fewer, but larger seeds. 

 The rubrinervis is in many respects a counterpart to 

 the gigas, but its stature is more slender. The spikes 

 and flowers are those of the lamarckiana, but the 

 bracts are narrower. Red veins and red streaks on 

 the fruits afford a striking differentiating mark, 

 though they are not absolutely lacking in the parent- 

 species. A red hue may be seen on the calyx, and 

 even the yellow color of the petals is somewhat deep- 

 ened in the same way. Young plants are often 

 marked by the pale red tinge of the mid-veins, but 

 in adult rosettes, from lack of sunshine, this hue is 

 often very faint. Both of these stout species have 

 been found quite constant from the very first mo- 

 ment of their appearance. I have cultivated them 



