THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 99 



Broad-sclerophyll Forest. 



Myrica californica.-(l) The thinnest of all the leaves studied. (2) Bifacial. Pali- 

 sade tissue of one complete and one partial layer, occupying one-third of the mesophyll; 

 in some places a suggestion of palisade layer next to the lower epiderm; sponge very loose. 

 (4) Stomata on lower side only, slightly elevated. (5) A sheath of tannin-filled cells 

 surrounds the bundles; occasional peltate glands in depressions on both surfaces. 



Castanopsis chrysophylla (fig. 22).— (1) The specimens examined are of var. minor, from 

 Monterey, and the leaves are probably somewhat more xerophytic in structure than those 

 of the typical tree-form of the northern Coast Ranges. (2) Bifacial. Mesophyll dense; 

 palisade tissue about four layers deep, occupying a little less than half the mesophyll, 

 composed of rather crowded oval or nearly globular cells. (3) Epiderm, no special fea- 



Fig. 22. — Castanopsis chrysophylla: section of leaf . X125. 



Fig. 23. — Quercus agrifolia: section of leaf. X125. 



Fig. 24. — Umbellularia californica: section of leaf. X125. 



25 



26 



Fig. 25. — Arbutus menziesii: section of leaf. X 125. 

 Fig. 26. — Quercus durata: section of leaf. X125. 



tures; incomplete hypoderm on both sides, mainly related to veins. (4) Stomata on lower 

 side only, slightly elevated, surrounded by collar-like ridges. (5) Tannin in cells sur- 

 rounding bundles and in hypoderm; struts of mechanical tissue from epiderm to epiderm, 

 following veins; multicellular trichomes covering lower surface, producing a golden fuzz. 

 Quercus agrifolia (fig. 23).— (2) Leaf bifacial but not perfectly so. Palisade tissue about 

 three to four layers deep, occupying about half the mesophyll and merging gradually into 

 the sponge, the cells of which are mostly elongated perpendicularly to the surface, thus 

 possessing palisade character; one or two incomplete palisade layers on lower side also. 

 (4) Stomata on lower side only. (5) Struts of mechanical tissue as in Castanopsis, but 

 more pronounced. 



