TENOPYR: CONSTANCY OF CELL SHAPE 73 
The cells near the base of the Witloof chicory leaf are appar- 
ently modified in their shape by their relation with the numerous 
veins. ; 
The lobing of the wild chicory leaf is not due to greater width 
of the cells in the lobes as compared with the constricted areas, 
but rather to the greater number of cells in the long axis of the 
lobe, which is almost at right angles to the midrib. This greater 
cell number is apparently due to a more rapid rate of division in 
the lobe cells as compared with those in the constricted regions 
(TABLE VIII). 
The cells of the leaves of the Witloof variety are larger than 
those of the wild chicory leaves, but the shape of the cells is almost 
the same in both varieties. The ratio of the length to the width of 
the Witloof cells is 1.01: 1, that of the wild chicory cells being 1.11: 1. 
SUMMARY AND CONCLUSIONS 
Cell size 
The cells of the plants above described show a considerable 
variability in size in the same tissue but that the average cell 
size for any one tissue of a species or variety, however, is a fairly 
constant and hereditary character, has been previously shown by 
Sanio, Amelung, Sachs, Strasburger and Conklin. 
The cell size of closely related species, as Linum usitatissimum 
and Linum angustifolium, may be the same, which agrees with 
the conclusions of Amelung and Conklin, or again, in closely re- 
lated varieties of the same species, as the common and Witloof 
types of Cichorium Intybus, the cell size may differ considerably, 
as was also proved tobe true incertain plants investigated by Gates, 
Keeble, Neilson Jones, Jakushkine and Wawilow, and Sierp. 
As Sanio, Jakushkine and Wawilow, and Sierp have already 
shown, the cell size in an organ depends in some degree on the 
stage of development of the plant at the time the organ was pro- 
duced. Thus the transitional leaves of Campanula rotundifolia 
and Lobelia Erinus which are developed after the basal leaves: 
have smaller cells, while the linear leaves, which appear latest, 
have the smallest cells. In both these plants, the average cell 
size of each type of leaf is a constant characteristic. Differences 
in the size of any given organ of a species are due to differences in 
