58 



SHORTER NOTES 



Mutations and Forms. — For nomenclatural purposes, I have 

 found occasion to divide variations (not subspecies) into two 

 groups, designated mutations and forms. There is nothing new 

 in this idea, but as it has not always been understood, some ex- 

 planation may be desirable. 



Mutations are variations in kind, probably always congenital, 

 and frequently (at least) atavistic. 

 Examples are : 

 i/^ Vionia Doiiglasii (Hook.) * mut. rosea [Clonatis Douglasii rosea 

 Ckll. West Amer. Scientist, 5:5. 1888), in which the 

 flowers are pink instead of blue. 

 Sanibiiciis microbotrys Rydb. mut. xantliocarpa and mut. oino- 

 carpa {S. racemosa xantliocarpa and omocarpa Ckll. Bull. 

 Torrey Club, 18 : 170. 1891), in which the fruit is of colors 

 different from that ordinarily found. 

 Lilinin montaman Nels. mut. pnlcJinini i^L. PJiiladelpJiicuni 

 pnlchrum, Aldrich, Science Gossip, Au 1889), in which the 

 usual spots on the flowers are absent. 

 Forms are variations in degree, frequently induced by external 

 conditions, and not usually atavistic. Examples are found in the 

 polymorphic species of Batrachiiini, the Po/j'gonnm-group, etc. 

 Mutations, as here understood, are not adaptive, unless acci- 

 dentally. Forms usually are adaptive. Just how far the charac- 

 ters of any given form are congenital cannot easily be ascertained ; 

 in one sense they always are, that is to say, the plant has the in- 

 herited power of responding in a given way to certain stimuli, if 

 it does not inherit what may be termed obligatory characters. 



Subspecies differ from the above in that they occupy different 

 environments (geographically or ecologically) and only connect 

 with the species in certain places, and then by intermediates. 

 The existence of numerous subspecies as here defined (e. g., in 

 mammals) seems to constitute a strong argument against the 

 mutation theory of species. On the other hand, polymorphism 

 shows how characters which in themselves are good enough to 

 base species (or even genera) upon may arise within specific limits, 



* Viorna Douglasii Clctualis /Jpui^'/asiiMw^V. II. lior.-Am. i :i.//. /. 1830. 



