278 



BOTANICAL GAZETTE 



[OCTOBER 



PRAXINUS AMERICANA 



Leaf 



Stem 



M 



T 142 ^ (124-159) 



UE. . . 11 = 8 per cent 



X 



l62 fJL (l42-l87) 



= 9 per cent 



P 



Sp.. . . 



52 

 68 



LE. . . 11 = 



OW... 1. s 



Cu. . . 0.7 



36 



48 



8 



14 

 68 



42 



59 =36 

 21 =13 



3 



1.8 



N.. 

 D.. 

 W.. 

 F... 



R.. 



M 



22.5 



X 



19s 



53 M(87) 51 m(72) 



3-7 



3-2 

 7.2 



3-9 

 4-5 

 7-3 



88 

 S3 



no 

 99 



3-5 



1-2 



X. — Epidermal cells of greater depth; X. — Differing from the majority in 



outer wall and cuticle thicker, ridged in number and size of vessels and more 

 the lower epidermis, most of the cells of rapid growth ; walls of vessels and fibers 

 the lower epidermis produced into short thicker; sclerenchyma and cork heavier, 

 conical hairs, the rest into long hairs In both walls of pith-cells thickened with 

 (ilf smooth); all tissue more compact; conspicuous canals, and outer cortex 

 palisade deeper, tending to develop four collenchymatous, features pronounced in 

 rows (M only two); vessels in the mid- X. 

 rib more numerous but not larger; walls 

 thicker; greater development of fibers 

 about the stele. Both have conspicuous 

 glands on the upper surface, and stomata 

 on lower surface only. — Figs. 6 and 7. 



6 



4 



5 



7 



Figs. 4-7.— Figs. 4 and 5, Celtis occidentalis: sections of leaves; fig. 4, mcsophytic 

 form; fig. 5, dune form; figs. 6 and 7, Fraxinas americana: sections of leaves; fig. "> 

 mesophytic form; fig. 7, dune form. 



