288 REVIEWS. 



Linnaeus, and by most systematists, upon different occasions. 

 Varieties are commonly designated by the small letters of the 

 Greek alphabet, a, (3, y, etc., and also by names when they are 

 pretty distinctly marked. Either the varieties, one or more, 

 may be appended to the species (that is, to the form taken as 

 the type, which usually must be the form originally described 

 under the name), and therefore be treated as aberrant forms; 

 or else the species is characterized as a group of forms, which 

 forms are classified and defined just as species are under their 

 genus. For instance, Mentha Canadensis is held to compre- 

 hend both a hairy and a smooth form, the two differing also 

 somewhat in other respects. Linnaeus founded the species on 

 the former ; and it is pretty well agreed that we are to refer 

 the species back to him, however it be limited. Now we 

 may either give a common character to the species, and then 

 distinguish var. a. villosa, and var. /3. glabrata ; or we may 

 characterize the species in general upon the originally named 

 form, and append the variety /3. glabrata. Either mode has 

 its advantages and is likely to be employed in certain cases. 

 The former classifies the varieties under the species, perhaps 

 more naturally, and exhibits the polymorphous character of 

 what we call a variable species ; and De Candolle considers 

 that it will prevail in proportion as the forms of a species 

 come to be well known ; the latter holds closer to the bibli- 

 ography. There is danger of some misunderstanding when 

 the two modes are used in the same work. In the " Synoptical 

 Flora of North America," the former mode is invariably 

 adopted, partly on the score of brevity. Either the originally 

 described form, or a medium or common form is taken as the 

 type, and the varieties are treated as departures from this. 

 Even when the specific character is drawn so as generally to 

 cover the varieties (as should be done as far as possible), 

 some form, and the history of the species generally indicates 

 what form, is kept in view as the norm or alpha. Of course, 

 except for cultivated plants, there is no knowing and no pre- 

 tence of determining which was the parent form, or in what 

 order the several varieties may have diverged from a pristine 

 stock. 



