70 TENOPYR: CONSTANCY OF CELL SHAPE 
from curves as irregular as these, the mean ratio of length to width 
in either species. 
This does not mean that the shape of the lower epidermal cells 
is the same in both cases. While the difference does not lie in the 
length and width of the cells, their outlines are quite different, 
the Cells of P. major being quite wavy in outline, while in both 
types of leaves. of P. lancéolata the cells are only slightly wavy in 
outline. The cells of the normally developed and the narrow leaves 
of Plantago lanceolata are practically the same in shape and size. 
LINUM ANGUSTIFOLIUM AND LINUM USITATISSIMUM 
The leaves of Linum usitatissimum are lanceolate, those of 
L. angustifolium are oblong or oblong-elliptical. The leaves of 
both species are sessile, acute and entire. Those of L. usitatissi- 
mum are about as broad, but at least twice as long as the leaves of 
L. angustifolium. The cells of the lower epidermis and the pali- 
sade cells were measured in each species. The measurements 
show a striking similarity in the cell shape of these two species of 
Linum. The cells of Linum usitatissimum are only .o4 longer 
than those of L. angustifolium, and show no relation therefore to 
the greater difference in their leaf dimensions. 
CicHorium INTyBUS 
The first leaves of the common type of Cichorium Intybus are 
entire but these are soon succeeded by other radical leaves which 
are distinctly lobed. The degree of lobing varies greatly in dif- 
ferent plants, but the leaves of any one plant are quite similar in 
shape. For this reason all the leaves of Cichorium Intybus whose 
cell shape was measured were selected from one plant, which had 
deeply constricted leaves. The Witloof type of Cichorium Intybus 
is a cultivated variety of chicory, which has large and relatively 
entire leaves. All the leaves of this type studied were taken from 
the same plant. These, as well as the leaves of the common type 
of Cichorium Intybus with which they were compared, were basal 
leaves. In both, the cells of the lower epidermis near the midrib 
and near the margin of the broadest part of the leaf, and midway 
between these two regions were measured and their two dimen- 
sions compared with the length and breadth of the leaves to which 
they belonged (TaBLe VII). 
