78 botanical gazette. [March, 



sion on both leaf surfaces in the direction of the shorter axis 

 (fig. 2). 



In passing from the periphery to the center, three distinct 

 regions are to be noticed: (1) A well-defined epidermal 

 system; (2) the mesophyll, made up for the most part of 

 somewhat large parenchymatous cells ; (3) the fibro-vascu- 

 ler bundle near the center. 



I. Epidermal system. — The epidermal cells in transverse 

 section show a slight irregularity both in size and shape. 

 The prevailing form appears to be elliptical, with the longer 

 diameter, in the line of the greater leaf axis, to the shorter 

 as two or three to one. In the depressions referred to above, 

 which occur immediately above and below the fibro-vascular 

 bundle, the cells become more nearly equal in their diameters, 

 and in some cases that in the direction of the shorter leaf axis 

 is the greater. At the extremities of the longer leaf axis the 

 epidermal cells are somewhat peculiarly modified. The ex- 

 treme cell is ordinarily much smaller" than those on either 

 side, which by their excessive development and remarkably 

 thickened inner walls separate it entirely from the underly- 

 ing parenchyma. In occasional cases this modification of 

 the adjacent cells is not so marked, but there is found instead 

 one or more rows of thick-walled "strengthening cells," ex- 

 tending from the apical cell back into theparenchyma. This 

 arrangement is evidently a special one, as nowhere else does 

 the epidermis show the slightest tendency to become of two 

 layers, and at this point the mode of its occurrence is such 

 that it probably can not be referred to this condition. In 

 these smaller apical cells, the walls are of comparatively 

 great thickness, almost obliterating the cell cavity. No 

 marked differences are to be observed in this section between 

 the epidermal cells of the outer and inner surfaces, unless it 

 be that m the latter the average cell length is less than in the 

 former. (See figs. 2, 3, 4 and 5.) 



A surface slice (fig. 6) shows the epidermal cells to be of 

 somewhat irregular outline, with their diameters of varying 

 proportion to each other. They are, however, more nearly 

 isodiametnc than would be expected in a plant with narrow 

 linear leaves, in which case, according to de Bary, "the lon- 

 gitudinal diameter is greatly extended."' The outer walls 

 are heavily cuticuanzed and in nearly equal degree through- 

 out the outline of the leaf. The cuticula? layers are extreme- 

 ly_ dense and tough. T hejion-cuticularized layer is rela- 

 te Bary, Comparative Anatomy of Phanerogams and Ferns, p. 30. ' 



