64 University of California Publications in Botany [VOL. 9 



These 30 genera account for 275 species, leaving 195 genera of 

 minor importance among which to divide the 328 species of flowering 

 plants not included within the great genera above listed. Of these 

 195 genera, 112 are monotypic, each having but a single species. The 

 remaining 83 genera divide 216 species and have a genus-species ratio 

 of 2.6. Perhaps a better idea of the significance of a comparatively 

 few leading genera may be gained if percentages are compared. When 

 this is done, it appears that : 



13.3 per cent of the genera include 45.6 per cent of the species; 

 36.9 per cent of the genera include 35.8 per cent of the species; 

 49.7 per cent of the genera include 18.5 per cent of the species. 



Summarizing the data here reviewed we find that the 633 vascular 

 plant species of the boreal region of the Sierra are segregated into 



(a) 5 families of pteridophytes with 14 genera and 20 species; 

 (6) 1 family of gymnosperms with 4 genera and 10 species; 

 (c) 51 families of angiosperms with 225 genera and 603 species, which are 

 grouped in 



(1) 30 genera of major importance, each with 5 or more species and 



totaling 275 species; 



(2) 83 genera of minor importance with 216 species; 



(3) 112 monotypic genera. 



Besides those plant groups which, in the writer's opinion, are suf- 

 ficiently marked to deserve recognition as species, there are in the 

 flora of the higher Sierra Nevada certain less well defined congeries 

 variously called subspecies, varieties, and forms, which in the aggre- 

 gate raise the total number of plant groups requiring nomenclatural 

 differentiation to 682. 



GEOGRAPHICAL ANALYSIS OF THE BOREAL FLORA OF THE 

 SIERRA NEVADA 



These 682 more or less well marked floristic units, which in the 

 aggregate make up the plant population of the higher Sierra, have 

 unequal ranges. Some are endemic within the Sierra ; some have their 

 presumable point of origin within our limits but are now more or less 

 widely spread beyond its borders as emigrants; others are certainly 

 immigrants from adjacent or more remote areas. Comparing the 

 known ranges of these high mountain species, varieties, and forms, 

 we find 



