384 Origin of Each Species Considered Separately. 



secondary stems is formed. Biennial plants are in every 

 respect stronger and bear larger fruits with better seeds. 



But the most characteristic feature of this species is 

 its smooth shining dark-green narrow leaves. 



The young rosettes are recognizable by this char- 

 acter (Figs. 81 and 82), and can easily be distinguished 

 by means of it from the species by which they happen 

 to be surrounded (Fig. 52, p. 293). 



The leaves are not very narrow at first ; in fact they 

 do not become so until the rosettes are 2 or 3 months 

 old. This feature gradually becomes more pronounced 

 during the summer whether the plant remains in the 

 rosette stage or develops a stem. The midrib of the leaf 

 is broad and like the leaf stalk is of so pale a green that 

 it might almost be called white, and has not a trace of 

 red color in it. The leaves of the full grown rosette have 

 long petioles and are about four times as long as they 

 are broad or even narrower. There are no unevennesses 

 on the blade nor is there that pale green bloom on them 

 which is characteristic of O. alhida and 0. rtibrinervis ; 

 they are almost absolutely smooth and very different 

 from those of Lamar ckiana in their dark green color. 

 Indeed, scintillans bears very little resemblance to its 

 parent species except in its flowers. 



The leaves of the stem (Fig. 54, p. 295) resemble 

 those of the rosette in all essential points and so do not 

 require any special description. 



In regard to the mode of its origin 0. scintillans re- 

 sembles O. gigas and O. semilata in being one of the 

 rarest types. It has only arisen 14 times altogether as 

 a mutation. Although most of these instances have al- 

 ready been described it is worth while summarizing them 

 all here. 



