THE KANSAS UNIVERSITY 

 SCIENCE BULLETIN. 



Vol. IX ; No. 21.] SEPTEMBER, 1915. [ v I ho xi e x s nTIi 



Anatomy of Platanus occidentalis. 



MAUDE MARIE BAIRD. 

 Plates LXV-LXXVI. 



THE natural habitat of Platanus occidentalis is the flood 

 plain of streams. The tree from which the material for 

 this work was obtained is growing upon the campus of the 

 University of Kansas, on prairie land which, though sheltered 

 from the south winds, is at a considerable elevation above the 

 Kansas river a half mile away, so that its water supply is 

 less than it would receive in its natural habitat. This condi- 

 tion may have affected its anatomical structure to some extent. 

 Miss Anna M. Starr ('97) has shown that there is a marked 

 difference between members of a species of plant growing in 

 mesophytic situations and members of the same species grow- 

 ing in xerophytic situations. She gives the following inter- 

 esting comparison of Platanus occidentalis growing in a swamp 

 habitat and the same plant which, by increased length of stem, 

 has been able to keep pace with a moving dune which is passing 

 over the place where it is growing. 



In the following table S stands for the swamp form and X 

 stands for the dune form : 



LEAF. 



S. X. 



Thickness 152 ,"- 199 Z^ 



Thickness of upper epidermis 23 =15% 25 =12% 



Depth of palisade 52 =34% 63 =32% 



Depth of sponge 62 =41% 92 =46% 



Tickness of lower epidermis 16 = 10% 19 = 10% 



Outer wall of epidermis 4 2.8 



Received for publication June 10, 1915. 



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