152 Gibson . — -Contributions towards a Knowledge 
case of that general cuticularization which takes place on the 
walls of cells exposed to air and the annular nature of the 
cuticularization as a secondary phenomenon resulting from the 
elongation of the endodermal cell following on the excessive 
development of the lacuna in this region. It ought to be 
remembered in this connexion that the endodermal cells con- 
tain no chlorophyll, although the pericycle on the one side and 
the inner cortical cells on the other both contain chlorophyll. 
Vladescu suggests that these endodermal cells are conductive 
in function ; they are undoubtedly supporting as well. 
The pericycle is one layer deep, sometimes two, and contains 
chlorophyll (PI. IX, Fig. 2). [It ought to be stated that in this 
and all subsequent cases the sections described were taken 
from stems of as nearly as possible equivalent age.] The pro- 
tophloem elements are few in number. The elements described 
by Janczewski as occurring just within the pericycle and as 
having the sieve-tubes radially arranged round them, are, it 
seems to me, simply protophloem-elements in process of 
occlusion. The sieve-tubes are two layers deep dorsally and 
ventrally, although opposite the marginal protoxylem-areas 
one imperfect and broken layer occurs. One or two layers of 
elongated parenchyma separate the sieve-tubes from the 
xylem, which latter is composed entirely of tracheides. 
Accounts fundamentally similar to that given above have 
been published by Strasburger, Janczewski, Treub, and others. 
2. Selaginellagrandis, Moore. Baker’s Handbook, No. 243. 
This large and beautiful species has a short decumbent 
stem, rooted at close intervals, from which thick erect shoot- 
axes arise. These are unbranched for a foot or so and 
then are copiously branched and dorsiventral. The creeping 
portion and erect shoots are fundamentally similar in structure. 
There is one large ribbon-like stele bearing marginal and 
dorsal protoxylems, as in X Martensii , and arising in a quite 
similar manner to those in that species. There is an epidermis 
and cuticle, a thick hypodermis, and a cortex of thick-walled 
pitted cells. Those next the lacuna are narrow and tubular, 
deeply pitted and enclosed in a siliceous deposit. These cells 
