446 MESSRS. J. PARKIN AND H. H. W. PEARSON ON THE 
“dry” patanas, and nineteen are common to both. We have 
thought it advisable to reduce these three groups to two by 
distributing the plants of the last-mentioned amongst the first 
two, according as the material for examination was collected in 
the wet or dry region, since in only two cases were specimens 
gathered and preserved in spirit from both kinds of patana. 
These are Lobelia nicotianefolia and Osyris arborea. Con- 
sequently in this section of the paper each of these plants is 
counted as two, one belonging to the wet region and the other 
to the dry. This brings the total number of plants for com- 
parison to eighty-two, of which forty-two are considered as “ wet ” 
patana and forty as “ dry” patana plants, thus nearly equalizing 
the two groups. In theTable the figures for Lobelia nicotianefolia 
and Osyris arborea are the mean of the two sets of calculations. 
Estimations similar to those given below have been made for 
the three categories separately, but it seems superfluous to 
record them here, for in no case are they contradictory ; e. 9., the 
average depth of the epidermis of the wet patana plant is greater 
than that of the dry patana plant when the species are divided 
into the three classes, and it still remains greater when they are 
reduced to two classes ; such holds good for the other averages. 
(1) Depth of the Upper Epidermis (exclusive of the thickness of 
its outer wall). 
Average depth for w.p.* .. 33°4 p. 
” ” d.p. oe 26°0 pe 
The w.p. has therefore on the whole a deeper upper epidermis 
than the d.p.—a result hardly to be expected in the light of a 
water-storing function for the upper epidermis. A factor, dis- 
cussed below, which must be taken into account, is that the 
arching of the outer wall is commoner amongst w.ps. This has 
already been shown to be associated with a deeper epidermal cell. 
Therefore, other things being equal, the tendency would be for 
the w.p. to have a deeper cell than the d.p. The difference, 
however, appears too great to be fully explained in this manner. 
The ratio of the depth of the upper epidermis to the thickness 
of the mesophyll for w.p. is as 1:6°5; for the d.p. as 1:8; so 
the w.p. has a relatively as well as an absolutely deeper upper 
epidermis. 
* w.p. is short for “ wet” patana plant, and 
d.p. for “dry” patana plant. 
