88 HARSHBERGER— LEAF STRUCTURE OF [April 23, 



are hairy. Eleven of the strand species are diphotophylls, and of 

 these six have two rows of paHsade chlorenchyma. Only four of 

 the salt marsh species are diphotophylls, and each of them has two 

 palisade rows. Reference to the classification of sand strand and 

 salt marsh species given above will enable the student to pick out 

 other differences existing between the sand strand and the salt 

 marsh species, as regards their leaf structure. 



Bibliographic Notes. 



Little has been done in America to study the influence of envir- 

 onment upon the internal structure of plants, but a start has been 

 made and it is only a matter of time when a large amount of im- 

 portant data will have been collected for comparison and generaHza- 

 tion. As bearing upon the study of the sea strand vegetation may 

 be mentioned the following papers. Kearney has discussed in his 

 paper, " The Plant Covering of Ocracoke Island : A Study in the 

 Ecology of the North Carolina Strand Vegetation" (Contributions 

 U. S. National Herbarium, V: 280-312), the histologic structure of 

 plants found upon Ocracoke Island as sand strand and salt marsh 

 species. In this paper the following plants concern us : Spartina 

 stricta, Tissa marina, SoUdago scmpervircns, Aster subulatus and 

 Baccharis halimifolia. In a second paper, " Report on a Botanical 

 Survey of the Dismal Swamp Region" (Contributions U. S. Na- 

 tional Herbarium, V: 484-509), under anatomic notes, Kearney 

 discusses the leaf structure of some selected plants. None of these 

 plants actually concern this paper, except Pluchca fatida and Bac- 

 charis halimifolia. Edith Schwartz Clements, in a thesis submitted 

 to the faculty of the Graduate School of the University of Nebraska 

 for the degree of doctor of philosophy (June, 1904), gives a useful 

 historic resume of the study of leaf structure from an ecologic 

 standpoint and also considers in a detailed manner the structure of 

 about three hundred species collected in the Colorado foothills and 

 mountains of the Pikes Peak region of the Rocky Mountains with 

 reference to the surrounding physical factors, which were deter- 

 mined by careful instrumental readings. Lastly, Harshberger, in a 

 paper noticed above, discusses the leaf structure of some seventeen 



