1922.] REVISION OF CALIFORNIA ARCTOSTAPHYLI 77 



cast to the scenery which is very different from the tone of the green 

 colonies of Arctostaphylos patula, whilst both, forming impenetra- 

 ble thickets, have nothing habitally in common with the rough 

 mat of Arctostaphylos nevadensis over which one may walk. Each 

 of the various units in the Sierra Nevada, moreover, is restricted to 

 a certain zone or topographic area, capable of being rather definitely 

 defined in terms of climate and altitude, that is to say they are 

 habital units fairly in harmony with the physical factors. In the 

 Coast Ranges the segregation of Arctostaphylos units presents a 

 more embarrassing complex, since changes in soil and climate are 

 more local and more multiplied and involved. 



The evaluation of the species in this paper rests upon a basis 

 different from that hitherto employed in this genus. Important 

 weight is given to the character of the pubescence on the peduncles 

 and pedicels of the inflorescence and on the foliage, to the glandu- 

 losity or the lack of it, to the hue of the foliage, and to the nutlets. 

 Altho commonly thought of as unstable or ecological the pubescence 

 and its character give in this genus useful and often dependable 

 differentiae, as well as the glandular character or its absence. While 

 the definition of species on the basis of such minute characters is 

 scarcely ever satisfactory the species in this case have, in a most in- 

 teresting way, been stabilized by support derived from neglected 

 but yet striking facts of their life history. In other words, the species 

 as segregated by the characters above indicated, are further fortified 

 by the facts of their biological reaction to fire and this character, 

 it is to be emphasized, does not cut across the characters described 

 above and used as initial differentiae, but parallels them closely. 

 Certain species are killed completely by chaparral fires and depend 

 exclusively upon seed for regeneration in their area. Other species 

 crown-sprout after fire and develop in various ways heavy root 

 crowns or broad tabular structures at the surface of the ground. 

 In small groups of closely related species, groups so close that the 

 component units have been defined only by critical reference to 

 the minute characters of pubescence and glandulosity — the units 

 of such groups will nevertheless show the strongest difference in 

 their reaction to destructively high temperatures in a chaparral 

 fire and display decisive cleavages which parallel the somewhat 

 obscure structural differences. 



1. A. glauca Lindl. The characters of recognition for this 

 species are its glaucous foliage, large viscid berries and globose 

 stones, the last being a very striking mark. While the large solid 

 smooth stones are very characteristic, small almost spindle-shaped 

 stones acute at each end may sometimes be found on the same shrub 

 with fruits containing large globose stones. Again an entire shrub 

 may bear only the former type of stone. This state appears in some 

 cases at least to be connected with under-nutrition. 



Arctostaphylos glauca is common in Southern California and is 

 not infrequent in the inner South Coast Ranges. It has sometimes 



