50 STOKESIA CYANEA. BLUE STOKESIA. 



for separating plants which by their whole aspect appear to be 

 closely related. 



Turning now to the morphologic side of our subject, we find 

 that the manifestation of the transforming power in the conver- 

 sion of leaves to involucral scales is remarkably regular in the 

 Stokcsia. In many of the Composites there are no gradations 

 whatever between the root-leaves and the involucre, or, in other 

 words, the stem is quite naked. In our plant, however, the leaves 

 are not only scattered all along the stem, but we may readily 

 perceive a gradation in their development from below upwards. 

 The lower leaves have entire edges, the next following have a 

 few bristle-like teeth near the base, and those still higher are 

 gradually shortened, with the number of teeth increasing in 

 inverse proportion to their size. But even when the leaves have 

 reached that period immediately preceding their transformation 

 into florets, they look more like small leaves than involucral 

 scales ; and they retain this character to the very last, for even 

 when the seed is quite mature, and when in other Composites 

 the scales would be dry, the outer ones of the Stokesia (see 

 Fig. 3) preserve their green color. 



An interesting fact connected with this plant is that it is the 

 only species of the genus, and that the genus itself does not 

 seem to be very closely allied to any of its neighbors. Those 

 who are interested in the theory of evolution, and believe that 

 every species has been derived from some other species by slow 

 and almost insensible modifications of structure through count- 

 less ages, would therefore say that many of the links which con- 

 nected our species with its parent form must have been lost. 

 With the theory of evolution still in mind, we might even 

 hazard a guess that the race of the species is nearly run, and 

 that it is doomed soon to die out altogether. This " guess " is 

 based upon the fact that the plant shows very little inclination 

 to vary, which may be interpreted as an inability to develop fur- 

 ther. The only variation we have ever noted has been in the 

 average height of the plants from different localities. Our plate 



