184 Gibson . — Contributions towards a Knowledge 
folia . There is an epidermis with cuticle and a very weak 
hypodermis (not more than two layers thick in the material 
I possess), and a large-celled thin-walled cortex, the cells of 
which become smaller towards the lacunae. There are three 
lacunae, each containing one stele with marginal protoxylems. 
The lacunar tissue shows a'n interesting modification (PL XI, 
Fig. 63). The endodermal cells are stout and long, and run 
direct from the pericycle to the cortex. The lacunar space 
is, however, filled by a loosely-arranged succulent parenchyma 
of rounded chlorophyll-bearing cells, having no connexion with 
the endodermal cells. 
The pericycle is one to three layers thick, and has a promi- 
nent cuticle. Protophloem-elements occur here and there, 
especially opposite the marginal protoxylems. The sieve- 
tubes pass quite round the xylem — one layer deep opposite 
the protoxylems, and two layers deep elsewhere. The sieve- 
tube layer is imperfect or wanting opposite the marginal 
protoxylems of the median stele. One or two layers of phloem- 
parenchyma separate the sieve-tubes from the xylem. 
47. Selaginella Mettenii , A. Br. Baker’s Handbook, No. 
102. 
This species is believed by some systematists to be 
a hybrid between X. inaequalifolia and X. uncinata. The 
anatomy of these two species, so far at least as the stem is 
concerned, is sufficiently distinct, as has already been shown, 
and one would expect to find intermediate characters in the 
hybrid, if hybrid it be. I cannot say I have found such in 
the stem of X. Mettenii . The stem is regularly tristelic, and 
the course and mode of fusion of the steles is precisely that 
already described in the case of X. inaequalifolia (PI. XI, Fig. 
64) . The median stele is strap-shaped, and bears two marginal 
protoxylems ; the dorsal and ventral steles are rounded, and 
generally, when small, carry one protoxylem each (PI. XI, Fig. 
65) . The epidermis and cuticle are succeeded by two to three 
layers of stereome. The cortex is large-celled, the cells as 
usual becoming smaller towards the lacunae. The trabeculae 
consist of endodermal cells, with or without clusters of green 
