288 



BOTANICAL GAZETTE 



[OCTOBER 



PTELEA TRIFOLIATA 



Leaf 



Stem 



M 



T .. 

 UE. 

 P .. 

 Sp. 

 LE. 

 OW 

 Cu . 



147 M (131-156) 



14 

 42 



9 per cent 



■ • 



= 29 

 78 =53 



13 



9 



1 .2 



thin 



X 



185 M (177-193) 



18 =10 per cent 



56 =30 



95 =5i 

 16 =9 



4.8 

 i-3 



M 



X 



N.. 

 D .. 

 W.. 

 F... 

 L... 

 R .. 

 C .. 



51 



5i 



53 M (73) 55 A* (82) 



2 . 2 



8.4 

 2-3 



3-i 

 2.9 



7.2 

 4-7 



50 



S3 



X. — Hairs abundant on lower surface 



(none in M): 



Agreeing with the majority, except 



dermis that collenchyma in outer cortex may 



slightly larger in surface; side walls on be no heavier in X.— Figs. 28 and 29. 

 both surfaces plane and cuticle ridged 

 (in M wavy and only slightly ridged); 

 palisade, sponge, and midrib as in other 

 X. One tree in an especially exposed 

 situation, near the top of a wind sweep 

 leading up from the lake, probably once 

 a mesophytic pocket, had a more pro- 

 nounced structure than the one figured; 

 the leaf averaged 210 m in thickness, with 

 an outer wall 6 . 4-8 m, heavily cutinized. 





\ 



\ 



28 



Figs. 28-29.— Ptelea trifoliata: sec- 

 tions of stems; fig. 28, mesophytic form; 

 fig. 29, dune form. 



29 



