- d 
AND ANATOMY OF THE STEM OF LYCOPODIUM. 21 
amount of variation has been observed in the stems of L. complanatum ; in some sections the 
phloem- and xylem-bands are quite parallel and horizontally situated, in others the bands 
bend outwards towards the ventral side in a V-shape, and at times one or two phloem- 
patches are isolated by xylem. The vascular structure of L. alpinum (Pl. 3. fig. 9 and 
Pl. 4, fig. 15) is also very variable, and while on the one hand it differs very slightly, if 
at all, from the irregular arrangement observed in Z. complanatum, on the other hand 
there is a great tendency to form isolated phloem-patches or phloem-islands ; and in 
other respects, notably the irregular differentiation of the xylem near the apex, it forms 
a connecting-link with the second group of Lycopods which is described later and which 
is characterised by the separation of distinct phloem-islands. In certain longitudinal 
sections of L. complanatum some of the inner cortical cells showed definite but not very 
obvious spiral thickenings. "These are shown in PI. 4. fig. 16, which indicates the spiral 
markings and the pits which oceur in the cortical cells, also the general appearance of 
_ the endodermis, pericycle, and vascular tissues. In view of the difficulty of deciding by 
means of external morphological features the distinction between L. complanatum and 
LL. alpinum, an attempt was made to get an anatomical distinction based upon the 
occurrence of these cells with spiral markings; but they were not distinguishable in 
some specimens that were definitely assigned to .L. complanatum, and a better criterion 
would seem to be the greater tendency to irregularity in the stem of L. alpinum. In 
this connection Mr. G. C. Druce was kind enough to supply me with specimen portions 
of English plants referred to L. complanatum. A very great similarity is apparent, in 
the case of all three species, in the smaller branches, which generally show a tetrarch 
structure. The cortical cells have their long diameter approximately horizontal, and the 
anisophyllous arrangement would seem to justify placing them in the same group. 
LYCOPODIUM OBSCURUM, Linn. 
This species is placed by Mr. J. G. Baker in the cernuum group, which contains erect 
species with a tree-like habit, and will be known to all botanists who are familiar with 
the rock-garden at Kew. The anatomical characters of this species are very similar to 
those of L. clavatum, and differ considerably from those of L. cernuum, which, as will 
be seen later, are highly specialised. The erect stem bears a number of roots at the base, 
and alternating pseudo-whorls of five or six leaves; on the ultimate branches there are 
alternating whorls of three leaves. The arrangement of the bundles in the smaller 
branches is tetrarch, so that externally and internally the symmetry is radial; but in the 
stem the number of protoxylems varies from nine to eleven, and the dorsiventral 
structure is similar to that noted for L. clavatum. 
LYCOPODIUM INUNDATUM, Linn. 
The habitat of this plant is well known; it occurs in swampy ground close to ponds 
and lakes. It is the only British form which is not subalpine, and may be found in 
several districts in the south of England. An important character is the presence of 
mucilage-cavities, which are described by Hegelmaier. Mr. J. G. Baker makes a small 
