11 



The subgenus Zerna as here emended contains the largest number of 

 our endemic species. They are widely distributed throughout our 

 region and are quite variable. 



ornUtianus 



pacificus 



porteri purgana kalmii 



vulqarix ciliatus richardsoni 



1 I I 



suksdorfii ramosus - Itevipes 



\ 



\ 



pumpeUia7nis erectus 



tnermis 



The subgenus CeratocMoa is apparently peculiar to the western por- 

 tions of North and South America, ranging from Alaska to Cape Horn. 



polyanthun aleutensis 



laciniaius 



\ 



carinutus ■ sitcliensis 



/ 

 \ / 



MARGINATUS : UllioloideS 



mbveluiinus 



It is impossible to represent by diagram, except in a ver^" general 

 way. the various relationships of a species. If the species diverged 

 along one or two lines, it would not be so difficult; on the contrary, 

 each shows more or less variation in several directions, so that the 

 typical form might more properly be regarded as a center from which 

 lines diverge in various directions. 



The results of this stud^^, which seem to us of most general scientific 

 importance, are those which give us a clew to the derivations and rela- 

 tions of the various species. It will be noticed that comparatively few 

 s3'nonyms are given under the species. By listing all the synonj^ms 

 given by various authors a very long but unreliable list might have 

 been made; it has seemed to us preferable, however, to restrict the 

 sj^nonymy to those names whose identity we have been able to Aerify, 

 either by the examination of the types or of authentic material. In 

 rare instances we have been obliged to accept the authority of those 

 who have had excellent opportunity for comparison and study of the 

 species referred to. 



DISTKIBUTION. 



The genus Br&mus is most widely distributed in the temperate and 

 mountain regions of the world. The genus seems to have reached 

 with us its greatest development in the Rocky Mountains. In the 

 tropics the species are almost entirely restricted to the higher moun- 

 tains. Some of the species are more or less distributed in arctic regions 

 also. The highest altitude reached by any species is about 4,000 

 meters, in the Rocky Mountains of Colorado. The species is Btoitius 



