90 THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 



a well-developed one. Small branches of 1 mm. or less diameter 

 were given off rather regularly, but at long intervals, all along the 

 main roots. These terminated in groups of mycorhizal rootlets 

 which were embedded in masses of sand-grains held loosely together 

 by hyphae. 



Fig. 19. — Root system of Adenostoma fasciculatum: upper drawing shows hori- 

 zontal, lower shows vertical distribution. In the latter case the roots 

 are arbitrarily drawn as if growing in one plane. 



Another excavation of considerable extent was made nearby to 

 learn something of the subterranean relations between the chaparral 

 shrubs and the lower plants that accompany them. The dominants 

 here were Adenostoma fasciculatum, Quercus durata, and Arctostaphylos 

 tomentosa. The individuals grew rather far apart, and therefore 

 the accompanying species were more numerous than usual. A second 

 stratum included Eriodictyon californicum, Rosa californica, Helian- 

 themum scopariu?n, Diplacus glutinosus, and Syrmatium glabrum, 

 low shrubs and half-shrubs. A third stratum comprised Micromeria 

 chamissonis, Gymnogramme triangularis, and a few grasses. Below 

 the surface only two strata were distinguishable. The upper one, 

 about 20 cm. in depth, with some humus, was fairly well filled with 

 the roots from the second and third aerial strata, together with great 

 numbers belonging to the dominants, which were most conspicuous 

 because of their large size. Below 20 cm. were found only the scat- 

 tered, deeply penetrating roots of the dominants. 



