BOTANY OF THE CEYLON PATANAS. 447 
(2) Thickness of the Outer Wall of the Upper Epidermis. 
Average for the w.p......... 5 p. 
” » Gp. ..eeeee, 6 p. 
So the d.p. has an appreciably thicker outer wall—a result to 
be anticipated. But this difference may be accounted for 
directly apart from any influence of climate or soil; for a 
hirsute covering is about twice as common amongst w.ps. as 
amongst d.ps.; and this has been seen to be associated with a 
thinner outer wall as a rule. About 30 per cent. of the w.ps. 
and 15 per cent. of the d.ps. have a hairy upper surface. Further, 
there are amongst the w.ps. quite as many with markedly thick 
walls as amongst the d.ps., e. g. fourteen plants of each have an 
outer wall 7 « or more in thickness, and three of each above 10°5 p. 
Consequently we are forced to the conclusion that in this 
particular the two sets of plants are very similar. 
(3) Depth of the Lower Epidermis (exclusive of the thickness of 
its outer wall). 
Average for w.p. .... 20°6 pw. 
” »» C.p......- 16°6 p. 
As in the case of the upper epidermis, so here the w.p. has a 
deeper cell than the d.p. The arching of the lower epidermal wall 
has not been strictly observed to say whether this influences the 
depth of the cell, as in the case of the upper surface. But if it 
does, it can hardly account for so great a dissimilarity in depth 
between the two classes of patana plants. 
(4) Thickness of the Outer Wall of the Lower Epidermis. 
Average for w.p.....--...- 3°7 p. 
9 3 d.p. wee wees 5'1 p. 
The thinner outer wall of the w.p. can be explained in the 
same way as for the upper epidermis. A hairy under surface is 
about twice as common amongst the w.ps. 
W.p... 24 plants, i.e. 57 p.c. with hairy lower surface. 
d.p. a 12 9 30 2 ” ” 
(5) Convewity of the Outer Wall of the Upper Epidermal Cell. 
Of the w.ps. twenty-eight out of forty-two, i. e. over 66 per 
cent., have been considered to have arched walls, nineteen of 
which have this feature pronounced. 
Of the d.ps., seventeen out of forty, i.e. 42°5 per cent., have 
arched walls, six of which have this feature pronounced. 
Thus, whatever may be its significance, it is commoner 
