Lycopodium complanatum and Lycopodium clavatum. 2 1 5 
Near the base of the first root of L. complanatum transverse sections 
show three groups of tracheides with phloem in the centre and extending 
between the xylem groups (PL XXII, Fig. 9). Sometimes two of the 
three groups unite, cutting up the phloem into a larger and smaller mass, 
but in both sporophytes of L. complanatum examined three separate 
groups of tracheides occurred in sections nearest the foot. Thus a change 
from diarch to triarch structure takes place in the first root. A similar 
change from two to three groups of xylem occurs in L. clavatum , where 
it was traced out and showed that one of the two groups of xylem became 
elongated laterally and a third group separated off from this. In this 
species a plantlet at about the same stage of development as the older 
sporophyte of L . complanatum (PI. XXII, Fig. 2) showed much the same 
arrangement of xylem and phloem, except that sections nearest the tip 
showed only a single group of xylem with phloem at one side, i. e. a col- 
lateral or monarch arrangement. Thus we may get one, two, and three 
groups of xylem in the first root. 
Immediately surrounding the vascular elements is a layer of cells 
which is clearly of cortical origin (see PI. XXII, Figs. 3, 5, 6 , and 9, 
cells marked x). This layer is called the pericambium by Bruchmann ; 
the cells are irregular in shape, and some of the walls show signs of ligni- 
fi cation, but in others this feature is absent ; sometimes the cells are 
considerably smaller and more rounded in shape than those of the sur- 
rounding cells, in which case they resemble more nearly the parenchymatous 
cells of the central cylinder. The pericambium is surrounded by an 
irregular band of cells, two or three cells in thickness, with walls lignified 
on all sides forming a protective sheath ; there is no distinct boundary 
between these two layers. Outside the protective sheath in the younger 
parts of the root lie two or three layers of large thin-walled cells with, here 
and there, small intercellular spaces. At the periphery is the piliferous 
layer consisting of similar thin-walled cells, some of which have grown 
out into root-hairs. (In L. clavatum the hairs are in groups of three or 
four, each group being formed from single epidermal cells.) De Bary 1 
states that only in Lycopodium can special hair-cells be distinguished 
from other epidermal cells of the root, and goes on to describe the 
formation of groups of hairs from a part of the lower end of an epidermal 
cell, which is cut off by an oblique wall as a small, cell, and undergoes 
division into 2-4 cells, each of which grows out into a root-hair. This 
evidently is the case in L. clavatum , but not in L . complanaHtm . Nearer 
the base of the root, the cells lying next to the protective sheath, to the 
extent of one or two layers, have very much thickened walls and small 
lumina (PI. XXII, Fig. 9), these are surrounded by large thin-walled cells 
with here and there, just without the thick- walled zone, intercellular spaces, 
1 De Bary, Comparative Anatomy of Phanerogams and Ferns, p. 60. 
