BOTANY OF THE CEYLON PATANAS, 451 
integerrima the stomata are confined to the lower surface of the 
leaf, which in other respects shows only feeble dorsiventrality. 
Both varieties of Hurya japonica as well as EF. acuminata show 
a great similarity in the structural characters of the cells of 
the upper and lower epidermis. In the leaves of Anaphalis 
marcescens, A. brevifolia, and Gaultheria fragrantissima the 
tendency to an isobilateral structure is found only in the meso- 
phyll. The three remaining species with semi-erect leaves—viz., 
Ligustrum Walkeri, Knoxia platycarpa var. hirsuta, and Litsea 
zeylanica—appear to be typically dorsiventral in structure. 
Thus of the thirty plants with erect or semi-erect leaves 
microscopically examined, ten have practically an isobilateral 
structure, ten others are isobilateral to some extent either in 
their epidermis or mesophyll, while the remaining ten are dorsi- 
ventral. An astonishing fact is that most of the dorsiventral 
ones are confined to the “dry” patanas: one only, Hedyotis 
Lawsonia, is restricted to the “ wet”? patanas, but shows an 
inclination towards isobilateralism in its mesophyll; Anosia 
platycarpa is common to both and possesses a well differentiated 
mesophyll, but the material was collected from the dry patanas. 
More remarkable still, these eight remaining dry-patana plants 
with erect or semi-erect leaves—viz., Actinodaphne stenophylla, 
Dodonea viscosa, Eugenia olivifolia, Glochidion zeylanicum, 
Lasiosiphon eriocephalus, Ligustrum Walkeri, Litsea zeylanica, 
and Myrsine capitellatum—are some of the most striking 
examples of dorsiventrality occurring amongst the whole group 
of plants anatomically investigated. Not only have they a 
marked palisade, but also a loose spongy tissue. The only 
feature in which the lower surface shows, as a rule, a similarity 
to the upper, is in the thickness of the outer epidermal wall. 
All these eight plants are shrubs or small trees. Can these 
plants have only recently taken to the erect habit and their 
structure not yet become modified ? 
The leaves of the two Monocotyledons, Cureuligo orchioides 
and Spiranthes australis, may be said to have an isobilateral 
structure; their mesophyll is practicaily homogeneous through- 
out and composed of cells hardly elongated at all. Since their 
leaves grow vertically or inclined to the vertical, they may be 
reckoned amongst the erect or semi-erect. 
To be consistent, let us see what plants other than those 
LINN. JOURN.—BOTANY, VOL. XXXV. 2M 
