ENUMERATION OF CONIFERS 171 



varieties, forms, lusus, and other subdivisions; all subdivisions 

 of a species are uniformly designated as "variety"; in gen- 

 eral usage this term is often dropped and the varietal name 

 directly joined to the specific name, e. g., Chamoecyparis pisifera 

 plumosa instead of C. pisifera var. plumosa, although this is 

 not strictly correct. No attempt has been made to substitute 

 new names for combinations like Chamoecyparis pisifera var. 

 plumosa aurea; such names have been retained for horticul- 

 tural purposes and placed in quotation marks to indicate that 

 the writer does not consider them botanical combinations. 

 They are, moreover, inadmissible under the International Rules, 

 because the name aurea cannot be used, since there is already a 

 variety aurea, namely C. pisifera var. aurea, Carr. According to 

 the Rules, a name can be used only once for a subdivision of 

 any one species, otherwise it would not be possible to designate 

 every subdivision of a species by only three names : the generic, 

 the specific, and the varietal name. The introduction of several 

 subordinate varietal names into a combination is justified only 

 if it is necessary or desirable to indicate the systematic position 

 of a certain form in a polymorphous species, but for the simple 

 designation of a plant the names of the intervening divisions 

 are often dropped. Combinations of four or more names are 

 cumbersome and have done much to discredit the Latin nomen- 

 clature of horticultural forms, which, after all, is the simplest 

 way to give a definite place to a plant and is understood the 

 world over. 



In the following systematic account the genera under their 

 families are arranged, as much as feasible, in a linear sequence, 

 according to their supposed natural relationship and under 

 each family a conspectus or key to the genera is given, chiefly 

 based on characters of the flower and fruit, to give a clearer 

 understanding of their relationship and to serve as an ex- 



