the Anatomy of the Genus Selaginella, Spr . 147 
The epidermal characters of the leaves of the erect stem are similar 
to those of the leaves of the creeping axis. Stomata occur on the 
aligular face, rarely along the margins. 
In section the mesophyll-cells are found to be homogeneous in 
character, and all are more or less elongated in the long axis of the 
leaf, forming a loose reticulum. In older leaves the aligular epidermis 
shows a tendency to separate from the mesophyll (Fig. 26). 
50. S. rupestris, Spr. (Figs. 27, 28.) 
As in the preceding species, the leaves are homophyllous, elongate 
lanceolate, with long spiny cusps, and margins fringed with unicellular 
spines. The ligular epidermis consists of elongated wavy cells with 
warty cuticle. No stomata occur on this face. The stomata on the 
aligular surface are confined to a groove situated above the midrib. 
In section the leaf is boat-shaped. A sclerotic hypoderma, one or 
two cells deep, occurs on the lateral wings beneath the epidermis. 
The mesophyll towards the aligular surface consists of much elongated 
branched and anastomosing cells ; towards the aligular face the cells 
are much shorter (Figs. 27, 28). 
51. S. oregana, Eat. 
The leaves in form and histological structure are almost precisely 
similar to those of S. rupestris. 
E. Lyallii-type. 
52. S. laevigata, Bak., var. Lyallii, Spr. (Fig. 17.) 
As in the case of the stem, this species differs somewhat in its leaf- 
structure from those already described. 
The ventral leaf is ovoid, equal-sided, and bluntly pointed with 
a smooth margin. The dorsal leaf is more elongated and lanceolate, 
without marginal spines. Both have descending wings adnate to the 
stem. 
The ventral leaf. The edge is composed of elongated thick-walled 
cells with little chlorophyll. The epidermis of both surfaces consists 
of elongated rhombic plates with wavy outlines. Several rows of 
stomata occur on the aligular face, close to and over the midrib, where 
the epidermal cells are much shorter. There are no stomata on the 
ligular face. The dorsal leafYi&s quite similar characters. 
L 3 
