THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 39 



three or four largest oaks and the two Arbutus clumps, together 

 with other trees outside the limits of the quadrat. 



If we should make a more general survey of the locality, we 

 would find that the quadrat represents average conditions faithfully, 

 except that another tree species, Umbellularia calif ornica, occurs 

 along the ravine-bottom and in side gulches. None of the trees 

 are tall, the mature of all species ranging from 7 to 12 meters in 



Fig. 6. — Quadrat at station 7, 10 meters square. The symbols 

 surrounded by double lines indicate trees of the domi- 

 nating stratum; the others represent the shrub stra- 

 tum; the herbaceous stratum was not charted. 



height. The oaks have mostly single trunks, those toward the 

 bottom of the slope being much larger than those above. One 

 specimen, 10 meters above the ravine-bottom, had a diameter of 

 8 m. The madronos mainly show the clump habit. Seedlings of 

 oak occur, but are very rare. No madrono seedlings were found. 

 The shade is nearly everywhere dense. 



Unlike the chaparral, the oak-madrono forest shows distinct 

 vertical zonation or layering. The dominants are the trees, and 

 beneath them there are two subordinate strata, one composed of 

 tall shrubs, the other of low shrubs and herbs. The first is few in 

 species, but one of these, Rhus diversiloha, is abundant. Others, all 

 relatively unimportant, are Berberis pinnata, Holodiscus discolor 

 arioefolius, Rosa californica, and Dirca occidentalis. With these 

 should be included a few frequenters of disturbed areas, such as 



