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BOTANY OF THE CEYLON PATANAS. 455 
plants of dry climates. The mucilage is not held in the lumen 
of the cell, but in the inner (basal) wall. This is enormously 
thickened, and composed principally of mucilage. It often 
presents a stratified appearance due to unaltered bands of 
cellulose. Such a wall can act as a water-absorbent and storer. 
In some cases all the epidermal cells may be thus modified, 
while in others specialized mucilaginous cells are scattered 
about. 
Several of the patana plants examined have such sacs. Their 
names are given below. 
Crotalaria albida (Pl. 12. fig. 9). The mucilage-cells are very 
numerous in both epidermal layers. Perbaps one out of every 
three cells has its inner wall mucilaginous. These cells, 
especially those of the upper epidermis, are very deep, pene- 
trating a long way into the mesophyll, the extra depth being 
wholly due to the thickness of the inner wall. 
Crotalaria rubiginosa. The mucilage-cells are much less 
numerous than in the preceding species and are, moreover, 
confined to the upper surface. This plant is also in other 
respects less xerophytic than C. albida. Neither is mentioned 
by Solereder as exhibiting this feature. 
Zornia diphylla. The mucilage-cells are numerous in both 
epidermal layers. 
Polygonum chinense (Pl. 12. fig. 8). The mucilage-cells are 
confined to the upper epidermis and are not very numerous. 
The genus is mentioned by Solereder as showing this feature. 
Lasiosiphon eriocephalus. The presence here of a mucilaginous 
epidermis is recorded by Solereder. The cells occur only on the 
dorsal surface and are numerous but not deep. 
Myrsine capitellatum. The mucilage-cells occur plentifully 
in both epidermal layers, but more so in the lower than upper. 
Eurya acuminata and the two varieties of E. japonica. The 
inner walls of both epidermal layers are uniformly somewhat 
thickened and mucilaginous—the mucilage is thus in these three 
instances not restricted to special cells. 
(4) Chloroplasts in the Lower Epidermis.—What appear to be 
chloroplasts exist in the lower epidermis of the leaves of 
Didymocarpus Humboldtiana (PI. 11. fig. 6, ch.) and Pedicularis 
zeylanica. Since fresh material of these plants has not been 
examined, it cannot be stated with absolute certainty from an 
investigation of the spirit-specimens that these bodies contained 
