160 JOURNAI, OF FORESTRY 



acters in common, known and as yet unknown, may be, and however 

 one or more of these related species may depart from characters origi- 

 nally supposed to be generic. The earlier concept of a genus was from 

 ■the viewpoint of special creation of each species; the present concept 

 of a genus is from the viewpoint of the theory of evolution. The 

 earlier concept may be compared to a box into which certain species 

 were fitted. The box itself, as an ideal, existed independent of what 

 might be ])ut into it, as witness Endlicher's excellent generic descrip- 

 tions with never a species mentioned. The later concept may be com- 

 pared to a colony of coral still held together by an ancient common 

 ancestry long since submerged. According to the earlier concept, a 

 genus could be more definitely described than can most genera accord- 

 ing to the later concept, but the species contained therein and conform- 

 ing to the characters assigned to the genus might be heterogeneous. 

 According to the later concept, characters assigned to a genus are ac- 

 cepted as a working hypothesis only and are changed or discarded as 

 further investigations throw more light upon the subject. Species are 

 assembled into genera according to the sum total of their morphological 

 resemblances. If a given character hitherto regarded as generic is not 

 common to such a related assemblage, or if it would bring together 

 species which by their want of morphological resemblances do not show 

 close relationship, this character is rejected as generic. Relationship to 

 a definite species (the type) is, according to the later concept, the bond 

 that holds a genus together. Hence, if the characters of one or two 

 species deviate from those common to all the others, they may still be 

 included in the genus if the sum total of their characters denote rela- 

 tionship. This later concept of a genus is both more fixed and more 

 flexible than the earlier concept. Both are matters of human judgment, 

 and the limits ascribed to a genus according to either concept varies as 

 human judgments vary. But with a definite species as the basis of a 

 genus, human judgments are more likely to be in accord than with an 

 ideal set of characters as the basis of a genus. In most genera de- 

 scribed in recent years a type species has been specified. But in the 

 genera of older authors, working under the earlier concept of a genus, 

 very rarely was a type designated. To adjust these older genera to the 

 prevailing concept, it is necessary to choose a type species. This is 

 often difficult because many genera of the earlier authors, especially 

 those of Linnseus, are made up of very diverse species. The genus 

 Finns of Linnfeus, for example, contained ten species, of which but 

 five belong to the genus Pinus as limited today. The other species be- 

 long to the firs, spruces, and larches, and one is the cedar of Lebanon. 



