+ 
356 BOTANICAL GAZETTE [may 
TABLE XIV. 
Median longitudinal section of Phoenix dactylifera, same as table XIV. 
The region from which measurements were made was halfway between the 
endodermis and cortex. The rows of cells apparently of maximum size 
were measured, 
MEASUREMENTS OF CELLS OF CONCAVE SIDE. 
Length 9 5 6 4 5 5 4 7 9 9 
Average length, — - - - - - ~ ae 
Width 12 13 12 II 13 ee 10 Il 10 
Average width, - - - - - 11.5 
MEASUREMENTS OF CELLS OF CONVEX SIDE. 
Length 20 18 20 17 18 20 21 18 = 4 WH 
Average length, - - . - - - 17-9 
Width 20 20 20 4 15 12 13 12 13 13 
Average width, = - . - - - . 15.2 
The curvatures of Phoenix offer distinct variations from those 
of Zea, of which the most striking is the extensive development 
of the cortex on the convex side of the root. 
The width of the layer external to the stele on the convex 
side is 30 and on the concave side 25. This difference is shown 
also by the measurements of the individual layers of cells. The 
radial diameters of the epidermal and sub-epidermal cells of the 
concave side are slightly in excess of those of the convex side, 
but it may be seen very plainly that the changes in these cells 
are purely passive and mechanical. The differences between 
the longitudinal diameters of these cells are of course in favor 
of those of the convex side, and the changes in form of the cells 
_of these layers are almost exactly in imitation of the folds of 
the bellows of an accordion. 
The force operative in producing curvature is to be found 11 
the cortical cells between the fifth and sixth layer from the epr 
dermis and the endodermis, and whatever the nature of the 
changes involved, it is found that an extension of the cells of 
the convex side in both a radial and longitudinal direction 
