104 THE BROAD-SCLEROPHYLL VEGETATION OF CALIFORNIA. 



Ceanothus papillosus 1 (fig. 33). —(1) Leaf strikingly revolute. (2) Bifacial. Palisade 

 tissue two to three layers deep, occupying one-half the mesophyll; sponge rather loose, 

 and many of the cells palisade-like. (3) Upper epiderm making one-sixth to one-fifth the 

 thickness of the leaf, composed of large cells filled with tannin; lower epiderm much thin- 

 ner, undulate, the cells also containing tannin. (4) Tannin in bundle-sheath, collenchyma 

 of midrib, and epiderm; sparse scattering of single hairs on both sides. 



Ceanothus rigid™ (fig. 34). — The description of C. cuneatus will answer for this species 

 in almost every particular. The slight differences noted are the smaller proportional size 

 of the entrances to the cavities and the greater elevation of the stomata above their imme- 

 diate surroundings. Gemoll (32) gives an illustration of the cross-section of the leaf of 

 C. crassifolius. It is very similar to C. cuneatus and C. rigidus. Probably all the species 

 of the subgenus Cerastes have leaves of the same general character. 



Ceanothus sorediatus (fig. 35).— (2) Bifacial. Palisade tissue two layers deep, occupying 

 half the mesophyll; sponge rather loose. (3) Epiderm much like that of C. papillosus, 

 but the upper is even more prominent, making from one-fourth to one-third the thickness 

 of the leaf. (4) Stomata on lower side only. (5) Tannin abundant in bundle-sheath, 

 collenchyma of midrib, upper and lower epiderm, and occasional palisade cells; very sparse 

 hairy covering on lower surface. 



Garrya elliptica.—(2) Bifacial. Palisade tissue about three layers deep, occupying half 

 the mesophyll, the uppermost layer composed of cells that are shorter than the others 

 and of twice the diameter;* sponge loose. (3) Upper and lower epiderm papillate; upper 

 cuticle by far the thickest of all those examined. (4) Stomata on lower side only, very 

 numerous and large, each surrounded by an imposing collar-like ridge. (5) Dense hairy 

 covering on lower surface; isolated sclerenchymatous cells of various shapes in the meso- 

 phyll. 



Arctostaphylos hookeri (fig. 36).— (2) Almost perfectly isolateral. Mesophyll composed 

 entirely of palisade tissue— about seven layers— slightly denser on the morphologically 

 upper side. (3) Cuticle very slightly thinner on the lower side. (4) Stomata on both 

 surfaces, sunken to the depth of the epiderm, with a small exterior chamber nearly closed 

 at the mouth. (5) Tannin almost throughout the mesophyll. 



Arctostaphylos pumila. — Very similar to the last, but not so perfectly isolateral; palisade 

 less dense in the lower half; stomata on lower side only. 



Arctostaphylos tomentosa. — Essentially like A. pumila. According to Niedenzu (70), the 

 stomata occur on both surfaces. My material does not confirm this, but such a difference 

 would not be strange in so variable a species. 



Arctostaphylos vestita (fig. 37).— Essentially like A. pumila; cuticle distinctly stratified. 



Eriodictyon calif ornicum (fig. 38).— (2) Bifacial. Palisade tissue very sharply differen- 

 tiated, about four layers in depth, occupying half or a little more than half of the meso- 

 phyll; sponge loose. (3) Upper epiderm papillate, with an exceedingly thin cuticle; lower 

 epiderm moderately invaginated between the veins, very thin here, not perceptibly cuticu- 

 larized, on the ridges opposite the veins resembling the upper epiderm; a very deep invagi- 

 nation on each side of the very large midrib. (4) Stomata on lower side only, confined 

 to the invaginated portions, slightly raised above their immediate surroundings. (5) A 

 dense hairy covering on lower surface, not confined to the furrows, but best developed there. 



Two species which belong to the broad-sclerophyll element of the 

 redwood-forest undergrowth have been studied for the sake of com- 

 parison. These, with the other members of the group, range far 

 north of California into the conifer forests of the Puget Sound region. 



Gaultheria shallon.—(l) Much like species of Arctostaphylos in general appearance, but 

 distinctly bifacial. (2) Palisade tissue one to two layers in depth, occupying one-third or 

 a little more of the mesophyll; sponge rather typical, very loose. (3) Upper cuticle moder- 

 ately thick, lower thin. (4) Stomata on lower side only, with a small exterior chamber 

 with constricted opening. (5) Tannin in bundle-sheath, almost throughout mesophyll, and 

 in upper and lower epiderm. 



1 A recent visit to the locality of collection seems to indicate that the material studied is 

 Ceanothus dentatus rather than C. papillosus. The two species are closely related. 



2 Apparently interpreted as hypoderm by Sertorius (see Solereder, 84, p. 433) ; but the cells 

 contain chloroplasts and are plainly a part of the palisade. 



