38 FITTOXIA, 



■ 



tlian it can sustain ; that tlie subtribes H 



ri 



Heternclironif^fP nrp to a fnni=;i(lfiraKlA rlAcn-pf 



that 



its 



by drawing the sabtribal line at color there are sundered 

 widely, in the books, some genera which in nature stand 

 closely side by side. And we have, on the Pacific coast, two 

 genera at least, Lessingia and Penfachteta, which are too 

 w^ell marked in habit and in morphological character to be 

 broken each into two on account of color. Each of these has 

 series of yellow-rayed and of white- or purple-rayed 

 species. There are also, in the same local flora, a few 

 instances in which Asteroid genera are too arbitrarily distin- 

 guislied by color only; cases in which white- or red-rayed 

 species are injudiciously made to form a separate genus, 

 instead of being added as a heterochromous series of species 

 to a homochronious genus. 



However, cases of this kind, in the tribe of composites now 

 under passing notice, are exceptional ; and the rule here is 

 that color is of generic value. In all the large genera of the 

 tribe, and those which enjoy a wide and general geographical 

 distribution, the distinctions of color are fundamental. Even 

 where, as between Solidago and Aster, there is the noticeable 

 but scarcely definable general difference of aspect, when you 

 are asked to name an absolute character by which to dis- 

 tinguish them, the difference in color of flowers is the only 

 only one that can be produced ; and that is constant. Nor is 



'^f< 



t, — ^ -^„.„^^ i.,,^ 



headed and long-rayed Golden-rods would be perfect Asters 

 if their rays were changed from yellow to white or purple. 

 If Aster midtijlorus had been dressed out in yellow instead 

 of white corollas, it would easily have found its place in 

 Solkhujo alongside S. nemorcdis. And although Solidago 

 bicolor has white rays, and is well conformed to the general 

 habit of the Golden-rod species, if its disk-flowers had but 

 shown a tendency to change to purple in age, after the manner 

 of tfiose of most or all true Asters, that mark, along with its 

 white rays, would have placed it in the genus Aster without 

 a dissenting voice from any botanist who ever made a special 



