130 Gibson. Contributions towards a Knowledge of 
numerous species. I was led from a study of the stem- 
structure to arrange the species somewhat differently from 
the scheme adopted by systematists. It will be interesting 
finally to see in how far the anatomy of the leaf supports or 
refutes the views expressed in that paper. 
Section I. Anatomy of Species. 
A. Martensii-Type. 
All the species coming under this heading have the epidermis 
on the ligular and aligular surfaces of the leaves dissimilar, 
and a mesophyll consisting of reticulate parenchyma. (It will 
be understood that, to save repetition, the chief differences 
in histology will alone be pointed out. Unless otherwise 
stated, the characters in the various species are those described 
in the type-species.) 
1. S. Martensii, Spr. PI. ix, Fig. 3 . 
Ventral leaf. The leaves are lanceolate, somewhat elongated, and 
unequal-sided with narrow, bluntly pointed apices. The margin consists 
of elongated sclerotic fibres, from which numerous unicellular tricho- 
mata arise. The cells of the ligular epidermis are polygonal, wavy 
on surface view, conical in section. No stomata occur on this face. 
The aligular face consists chiefly of elongated plate-like cells with 
sinuous margins, amongst which occur scattered sclerotic fibres. The 
stomata are in several rows over the midrib, and the epidermal cells 
are often sclerotic in the neighbourhood. Occasionally stomata occur 
on the lamina, near the margin of the leaf. Near the stomata the 
epidermal cells are considerably shorter. Cuticular warts occur on 
the surface of the marginal cells. 
Dorsal leaf. The leaves are ovoid oblique with well-marked apices, 
and the margins bear numerous unicellular trichomata. The ligular 
epidermis consists of elongated, wavy-bordered cells without stomata. 
The aligular surface consists of polygonal sinuous cells, peg-shaped 
in section, with numerous stomata. Very many of these stomata have 
their guard-cells surrounded by strongly thickened epidermal cells, 
especially on the walls touching the guard-cells (Fig. 3). 
