100 THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 



Querciis chrysolepis. — The specimens are from the shrubby chaparral form. Even so, 

 they exhibit less of xerophytic character than the last, in that they are more perfectly 

 bifacial and that the sponge is more typical. Otherwise they are essentially like those of 

 Q. agrifolia. 



Pasania densiflora. — (2) Bifacial. Palisade tissue about two layers in depth, occupy- 

 ing less than half the mesophyU; sponge not abundant, most of the space being taken up 

 by groups of large, thin-walled parenchyma cells, apparently water-storage tissue. (3) A 

 complete layer of hypoderm beneath the upper epidcrm and resembling it; lower epiderm 

 papillate. (4) Stomata on lower side only. (5) Struts of mechanical tissue like those of 

 the other members of the family. 



Umbellularia calif omica (fig. 24). — (2) Imperfectly bifacial. Palisade tissue two layers 

 in depth, occupying half the mesophyU, and an imperfect layer next to the lower epiderm; 

 large oil-cells in both palisade and sponge, many of those on the lower side being enlarged 

 elements of the epiderm (84, p. 703). (4) Stomata on lower side only. 



Arbutus memiesii (fig. 25). — (2) Bifacial. Palisade tissue of two complete rows, occu- 

 pying one-third or more of the mesophyU. (3) Lower epiderm minutely papUlate. (4) 

 Stomata on lower side only, with small exterior chamber formed by a collar-like ridge. 

 (5) Tannin very abundant, almost throughout the mesophyU. 



28 



Fio. 27. — Dendromecon rigidum: Bectioa oiXeai. X125. 

 Fio. 28. — Dendromecon rigidum: stoma. X375. 



Climax Chaparbai,. 



Quercus durata (fig. 26). — (2) Imperfectly bifacial. Palisade tissue about three layers 

 deep, making half the mesophyU; sponge rather loose, but cells palisade-like. (3) Lower 

 epiderm papillate. (4) Stomata on lower side only. (5) Tannin in lower epiderm and to 

 some extent in upper; struts of mechanical tissue as in Q. agrifolia. 



Berberis pinruUa. — (2) Completely bifacial. PaUsade tissue two layers deep, occupying 

 half the mesophyU; sponge fairly typical. (4) Stomata on lower side only. (5) Struts 

 of mechanical tissue associated with veins. 



Dendromecon rigidum (figs. 27, 28). — (2) Almost perfectly isolateral, in correlation with 

 its vertical placement. Palisade tissue on both sides of leaf, two perfect rows above, two 

 imperfect ones below, rather loose; sponge central, occupying one-third of the mesophyU, 

 loose. (3) Both upper and lower epiderm strikingly papiUate. (4) Stomata numerous 

 and large, on both surfaces, sunken in pits to the depth of the thickness of the epiderm. 

 (5) Struts of mechanical tissue associated with veins. 



Heteromeles arbulifolia. — (2) Bifacial. Palisade tissue about three layers deep, making 

 less than half the mesophyU; sponge abundant, rather typical. (3) Lower epiderm papil- 



