Lycopodium comp l an a turn and Lycopodium clavatum. 231 
and unlignified as in L. rufescens ; (3) singularly thin-walled bast, as in 
L.guidoides ; (4) bast with thin walls in the interior and thick-walled on the 
exterior, as in L. tetragonum. He includes L. complanatum in the same 
group as L. annotinum , L. clavatum , L. magellanicum , and L. alpinum , forms 
which are characterized by their very woody bast, slanting palisade cells, 
and strongly developed stomata. I was unable to detect lignification in the 
walls of the bast-cells of L. complanatum , but they appear thickened. 
A definite endodermis was not distinguishable in the leaves of 
L. complanatum , and the bundle elements seemed to gradually merge into 
the more loosely and irregularly arranged parenchyma forming the 
mesophyll. Stomata occur on both upper and under sides of the leaf of 
the young sporophyte. 
The leaves arise very close together, and are irregularly arranged in 
four rows round the stem. They begin as small projections formed by two 
or three of the epidermal cells near the apex growing in a radial direction, 
and rapidly dividing by periclinal and anticlinal walls. In the very early 
stage an apical cell appears, and from this cells are cut off for the upper 
and under side of the leaf, while periclinal walls cut off cells for the central 
tissue ; at the same time there is active division taking place at the base 
of the leaf, and while, after a time, the apical cell ceases to divide, inter- 
calary growth at the base continues until the leaf has reached its full 
length. At a very early stage the cells bordering the apex begin to 
elongate, forming the long tapering point characteristic of the mature 
leaves, and the differentiation of the vascular strand soon begins. In the 
stem the tracheides of the leaf-trace are the first to appear ; they occur 
at the periphery of the central stele and then run obliquely upwards through 
the cortex of the stem, extending towards the tip of the leaf, but never 
quite so far as the actual apex. 
Stomata are developed on both sides of the leaf, and, as the leaf grows, 
air-spaces become more numerous, especially in the lower region, and are 
connected with the air-spaces of the stem, the cortex of the stem passing 
insensibly into the bases of the leaves. 
The leaves of the young sporophytes of L . complanahim show con- 
siderable differences from those of the aerial part of the mature plants, 
both in arrangement and general structure. 
In the young sporophytes they are arranged in four rows in an 
irregular spiral manner, often two leaves occurring opposite or almost 
opposite each other, but at the base considerable internodes generally 
intervene. They are all linear lanceolate in form, the lower half of the leaf 
closely adhering to the stem. In the mature plant the leaves are crowded 
together, and fused with the stem in such a manner that one cannot tell 
where the leaf ends and the stem begins ; only a small portion of the leaf 
is free from the stem. They are arranged very regularly in four rows 
