486 CALIFORNIA ACADEMY OF SCIENCES. 



witli which it has been combined in later systematic works. 

 Thus viewed in all forms, they are densely branched, 

 shrubby plants, with smooth reddish bark, renewed annually 

 by an exfoliation of that of the previous season, which, by 

 the swelling of the branches at the time of growth in May 

 or June, detaches the old in loose flakes, showing beneath, 

 the light greenish new bark becoming tawny-red on expos- 

 ure, to go through the same process of decortication the next 

 season. In the sub-arborescent forms the branches thickly 

 set on the base of the irregular trunk, project their rigid 

 and crooked limbs in every direction, forming dense, almost 

 impenetrable thickets. 



The evergreen foliage, varying in tint from bright vivid 

 to dull green, or glaucous, is smooth, or roughly pubescent, 

 rarely tomentose, and usually entire, the different species 

 generally presenting well marked specific distinctions in 

 shape and texture. Of these, A. Andersoni, Gray, is excep- 

 tional in its frequent sharply serrate leaves, though in all 

 seedling plants observed, the earliest growth succeeding 

 the cotyledons is invariably serrate, in this respect cor- 

 responding to the interesting observations of Prof. Greene 

 in regard to the early growth of Priinus occidentalis on Sta. 

 Cruz Island. The usual vertical twist to the petioles, giving 

 the leaves a perpendicular direction, is one of the features 

 common to many shrubs in arid districts, with the obvious 

 result of checking evaporation by less direct exposure to 

 the vivid rays of the summer sun. 



The inflorescence always terminal on the growing shoots, 

 is provided for by fully formed buds of the previous season 

 protected by their characteristic bracts, thus prepared to 

 develop their delicate urceolate corollas as early as the sea- 

 son of growth will allow, in favorable seasons attaining a 

 full development by January or February. 



The usual form of inflorescence is a panicle, with more 

 or less extended or divaricate lateral and terminal racemes. 

 The subtending bracts are usually quite characteristic in the 



