a, 
BOTANY OF THE CEYLON PATANAS. 439 
marked off from the spongy (lower mesophyll), but that the one 
gradually passes into the other. 
Columns XJ. and XII. give the depth of the palisade and spongy 
tissues respectively. Blanks naturally occur in these columns 
when the mesophyll is isobilateral, or feebly differentiated. 
Column XIII. represents the ratio of the length of the palisade- 
cell to its breadth ; e.9., 65 means that the length of the cell in 
question is six and a half times its breadth. In the case of a 
two- or more-layered palisade the measurement was taken of the 
deepest layer, which is in nearly every case the uppermost. 
Column X1V. Here the amount of intercellular space in the 
mesophyll is roughly indicated ‘1’? signifies that the cells are 
loosely arranged and the intercellular space, therefore, con- 
siderable; “¢” compact, implies the converse; “v,” “8s,” and 
“f” stand for the qualifying adverbs “very,” “slightly,” and 
“fairly,” respectively. . 
IV. Generar SuMMARY oF THE ANATOMICAL CHARACTERS 
OF THE LEAF. 
Under this heading the data of the various columns of the 
table are discussed and summarized for the plants as a whole, as 
well as reference made to certain additional points in their leaf- 
anatomy not included in this table. 
(1) Depth of the Upper Epidermis (exclusive of the thickness of 
ats outer wall). 
The average depth of the upper epidermis for the whole of 
the plants included in the table is about 30 *. A considerable 
number have a deep upper epidermis, at any rate relative to the 
whole thickness of the leaf, suggesting that it possesses a water- 
storing function. Emilia zeylanica, Oldenlandia Heynei (Pl. 11. 
fig. 4), and Senecio ludens are extreme examples. It is perhaps 
of interest to compare the depth of the upper epidermis with that 
of the mesophyll. The average ratio for these plants is 1:7, te. 
the mesophyll has on the average seven times the thickness of 
the upper epidermis. Leaves in which the upper epidermis 
bears a large proportion to the whole thickness are very thin 
ones, such as those of Oxalis corniculata and Pouzolzia Ben- 
nettiana, in which the ratio is less than 1:2. Examples of the 
* The numbers given for averages, &c. are approximate, decimals not 
being used to more than one place. 
