THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 101 



late. (4) Stomata on lower side only, slightly sunken, with a small exterior chamber 

 formed by a collar-like ring. (5) Tannin in bundle-sheath and almost throughout the 

 mesophyll, abundant. Hypoderm has been reported by Gerard (see Solereder, 84, p. 303), 

 but I have been unable to find any. 



Adenostoma fasciculatum (plates 20b, 21a).— (1) Leaves needle-shaped, nearly terete, 

 the morphologically upper side flattish, the lower roughly semicircular in cross-section ; 

 bundles arranged in a rough circle, the main one being opposite the middle of the upper side. 

 (2) Palisade tissue about three layers in depth, equally developed on all sides, with wide 

 gaps below the stomata; sponge central, loose, sharply differentiated from the palisade. 



29 



Fig. 29. — Xylothermia montana: section of leaf. X125. 

 Fig. 30. — Xylothermia montana: stoma. X375. 

 Fig. 31. — Rhamnus crocea: section of leaf. X125. 



Fig. 32. — Ceanothus cuneatus: section of leaf; black indicates distribution of 



tannin. X75. 



(3) Cuticle very thick, equally so on all sides. (4) Stomata on all sides, with exterior 

 chambers of the depth of the cuticle, almost closed at the mouth and containing plugs of 

 granular material. (5) Veins surrounded by heavy sheaths of large cells which are filled 

 with tannin. Leaves from seedlings and sprouts are very different. These will be de- 

 scribed in another section (p. 109). 



Primus ilicifolia.—(2) Imperfectly bifacial. Palisade tissue about four layers deep, 

 making half the mesophyll, with one or two incomplete layers next to the lower epiderm; 

 sponge scanty. (4) Stomata on lower side only. (5) Abundant tannin in bundle sheath. 



Xylothermia montana (figs. 29, 30).— (2) A bifacial leaf of a novel type. Immediately 

 below the upper epiderm is a single layer of enormous cells elongated perpendicularly to 

 the surface, and extending from two-thirds to three-fourths of the distance to the lower 

 epiderm. They resemble palisade tissue both in profile and cross-section, and may perhaps 

 be regarded as a modified layer of such. They contain dense masses of tannin which com- 

 pletely fill the cavities, and which frequently come out whole or in pieces in the process 



