1 86 BOTANICAL GAZETTE. 



next undernea th the upper epidermis and appear to be special pro 

 vision against excessive evaporation and are in entire keeping with 

 the thick epidermis. They are thin-walled and contain abundance 

 of chlorophyll, though probably less than the proper parenchy- 

 matous cells next below them. These last-named parenchymatous 

 cells are, as might be expected, loose in their aggregation and show 

 numerous open spaces which are in apparent relation to the ad- 

 mission and escape of atmosphere and the contained gases of the 

 plant. The under surface of the leaf is raised into ridges or prom- 

 inences between which in the cavities so formed the stomata (h) 

 are placed under proteition of numerous inflected and variously 

 curled hairs (g). This mode of placing and protecting the stomata 

 is by no means uncommon, being found also in the Oleander, in 

 Banksia, and in Ceanotkus prostratus, to say nothing of many other 

 plants. Sometimes, at least, it is known to be associated with dry 

 habitats; often enough, at least, to suggest the inquiry as to 

 whether it may not be to prevent stomata which occupy such 

 cavities from becoming choked with dust or other foreign bodies. 

 This raises the question as to the meaning, from the standpoint of 

 evolution, of such elevations and depressions on the under surface 

 of the leaf. So far as I am aware they are never seen except in 

 hard-leaved plants, which leaves are also often further protected by a 

 thick coating of hair. Is all this a mere trace remaining of what 

 was once a more common structure, adapted to more variable or 

 more inclement (hot or cold) climate, before the elevations were 

 smoothed away and the hairs were rendered unnecessary by the 

 more genial conditions of present snrroundings? This is simple 

 conjecture on mj r part, but I cannot avoid thinking that it is not 

 far from the truth. — De. J. T. Rothrock. 

 Explanation of Plate II. — Eriodictyon glutinosum, Benth. 

 Figure 1. Typical pith cell X 240, from central part of pith. 

 Figure 2. Typical pith cell X 240, from outer part of pith. 

 Figure 3. Less common form of pith cell X 240, from outer part of 



pith. 

 Figure 4. Isolated cell X 240, from medullary ray. 

 Figure 5. Selerenchym cell X 240, found in the bast zone. 

 Figure H. Longer selerenchym cell X 240, found in bast zone, and 

 also along with woody fibre in interior of stem, 

 where it would be regarded as a thickened form of 

 wood parenchyma. 

 Figure 7. Typical cell X 240, from bast zone. 



Figure 8. More common form of bast cell as found in other plants. 

 Cinchona flava, though also occasionally in Eriodictyon. 



Figure 9. Bast (or selerenchym '?) cell X 120, longitudinal view. 

 Figure 10. Same X 240, transverse section. 

 Eriodictyon glutinosum, Benth. 



Figure 11. Leaf section; a, epidermis of upper surface showing 

 thick walls and pits; b, secreting gland backed by 

 striated cuticle; c, palisade cells; d, parenchym cells; 

 /', epidermis of lower surface; g, long hairs which 

 guard the stomata (h) seated in a cavity on the un- 

 der surface of the leaf. 



