THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 115 



The species of the next list are the shrubs that make up the chapar- 

 ral, which in extent and in number of species and of individuals 

 is far more important than the broad-sclerophyll forest. A further 

 point of contrast is the far greater number of species in the chaparral 

 which have a decidedly restricted range. To complete the picture, 

 the following species from List I should be added, since in shrub form 

 they have a more or less important place in the chaparral : 



Castanopsis chrysophylla minor. Quercus wislizeni frutescena. 



Quercus chrysolepis. Pasania densiflora echinoides. 



Quercus garryana. 



Considering the region as a whole, 4 genera, representing as many 

 families, are of paramount importance in the chaparral. These 

 are Quercus, Adenostoma, Ceanothus, and Arctostaphylos. They 

 are widely different in the number of species representing them. 

 Adenostoma, with the" most important single species, includes 2; 

 Quercus has 6 that are strictly chaparral forms; while in Arctosta- 

 phylos and Ceanothus I have listed 18 and 25, respectively. The 

 treatment of the last two genera is of necessity unsatisfactory, since 

 there is disagreement among taxonomists upon the fundamental 

 questions of specific limits and relationships. In both genera there 

 are groups of forms which are regarded by some authors as constitut- 

 ing single variable species. Within a group there are several forms 

 which may be species, varieties, or merely ecological variants. ^ It 

 seems better for the present purpose, in doubtful cases, to consider 

 the larger unit as the species, rather than to attempt to maintain a 

 number of so-called species, sometimes poorly defined, of uncertain 

 range, often known only from the type locality. It is not denied 

 that these variant forms are of the greatest ecological interest and 

 importance. At the present time, however, our knowledge of them 

 is in every way insufficient to make adequate discussion possible. 

 In the treatment of each genus I have, so far as possible, followed 

 the author who has given the most recent and complete taxonomic 

 account of the group concerned. These are Trelease (89) in Ceano- 

 thus and Abrams (2) in Arctostaphylos. In both cases I have omitted 

 a number of species of uncertain validity or range. 



In the list below I have attempted to indicate as accurately as 

 has been possible to determine, from personal observation, literature, 

 and herbaria, the range and degree of importance of each species of 

 the chaparral. In the case of the most important one, Adenostoma 

 fasciculatum, the range has been plotted on a map (plate 3). This is 

 fairly accurate, since it is based on a careful and widely extended 

 field study, supplemented by examination of literature and herbarium 

 records, and by notes from a number of persons possessing a wide 

 acquaintance with the vegetation of California. These sources 

 together yielded a total of about 250 known localities. 



