‘450 MESSRS. J. PARKIN AND H. H. W. PEARSON ON THE 
Intercellular space. 
w.p. with aloose mesophyll 24, z.e.57 p.c.; compact 11,z.¢. 43 p.c. 
d.p., % » 26,72.e.65p.c.; 5, 14, 7.e. 85p.c. 
A result hardly to have been anticipated that the d.ps. should 
have on the whole a looser mesophylli—more intercellular space 
—than the w.ps. This may be partly explained by the fact that 
there are more typically dorsiventral leaves amongst the d.ps., 
and that a marked palisade-layer may allow a looser spongy tissue 
beneath. 
VI. Remarks on THE StRUCTURE oF ERECT AND SEMI-ERECT 
LEAVES. 
Erect Leaves.—Twenty-seven species of Dicotyledons are 
recorded * as possessing leaves which have a permanently erect 
position. Fourteen of these have been anatomically examined 
and are included in the Table. Five—viz.: Polygala telephioides, 
Evolvulus alsinoides (Pl. 11. fig. 5), Striga lutea, S. euphrasi- 
oides, and Osyris arborea (Pl. 12. fig. 2)—are isobilateral in 
structure. Two others, Geniosporum elongatum and Rhodo- 
myrtus tomentosa, approach the isobilateral structure ; the former 
in distribution of stomata, feeble differentiation of mesophyll, and 
the depth of the cells and thickness of the outer walls of the 
upper and lower epidermis; the latter only in the undiffer- 
entiated character of the mesophyll. The remaining seven— 
viz.: Dodonea viscosa, Kugenia olivifolia, Actinodaphne steno- 
phylla, Glochidion zeylanicum, Hedyotis Lawsonia, Lasiosiphon 
ertocephalus, and Myrsin ecapitellata—are distinctly dorsiventral 
in structure, though erect in habit. 
Semi-erect Leaves.—Of the twenty-five species with semi-erectT 
leaves sixteen have been studied in the Laboratory, and in these 
the correspondence between structure and recorded position 18 
more marked than in the case of the “erect” leaves. Five species— 
Hypericum mysorense (Pl. 11. fig. 3), Crotalaria albida, Tephrosia 
tinctoria, Bupleurum mucronatum (P). 11. fig. 1), and Swertia 
zeylanica—have leaves more or less isobilateral in structure. 
Those of Emilia zeylanica are almost as strongly isobilateral, but 
the upper epidermal cells are rather deeper than those of the 
lower, and by far the larger proportion of the stomata are found 
on the under surface. In Ewacum zeylanicum and Caralla 
* Pearson, Journ. Linn. Soc., Bot. xxxiv. (1899) p. 327. 
t Pearson, loc. cit. p. 328. 
