1 62 Gibson . — Contributions towards a Knowledge 
21. Selaginella denticulata , Lk. Baker’s Handbook, No. 12 
In anatomical characters the stem of this species ap- 
proaches so closely to X. helvetica that a separate description 
is unnecessary. 
22. Selaginella pilif 'era, A.Br. Baker’s Handbook, No. 210. 
This species is very closely related in anatomical struc- 
ture to X. lepidophylla. The epidermis is rather more distinct 
than in that species. The distal cortical cells are thin-walled. 
The pericycle is one to two layers deep, and there is one 
layer of flattened sieve-tubes, absent opposite the marginal 
protoxylems. 
23. Selaginella patida , Spr. Baker’s Handbook, No. 52. 
This species resembles closely 5 . serpens in the minute 
anatomy of the stem. The arrangement of protoxylems and 
leaf-traces is as in that species. There is little or no hypo- 
dermis. The cortex has small intercellular spaces in the layers 
next the lacuna. The trabeculae consist of endodermal cells 
articulating usually with two elongated cortical cells. The 
pericycle is one layer deep, though occasionally two layers 
occur. The phloem is small in amount, especially on the 
ventral side of the stele, where not infrequently the pericycle 
abuts on the xylem. One layer of sieve-tubes, often inter- 
rupted, is separated normally from the xylem by one or 
(rarely) two layers of parenchyma (PI. IX, Fig. 18). 
24. Selaginella convoluta , Spr. Baker’s Handbook, No. 209. 
In the anatomical structure of the stem this species is 
near S. lepidophylla. There is a thick hypodermis and an inner 
cortex of tubular cells with small intercellular spaces. The 
trabeculae are of the usual type. The pericycle is one or two 
layers deep. One or (occasionally) two layers of sieve-tubes 
occur dorsally and ventrally; they are wanting, however, 
opposite the marginal protoxylems ; they are separated from 
the xylem by several layers of parenchyma. The xylem is 
massive, and has the usual arrangement of protoxylems. 
25. Selaginella albonitens.S^r. Baker’s Handbook, No. 147. 
The structure of the stem of this species is almost iden- 
tical with that of X. apus . The sieve-tube layer passes 
