AND ANATOMY OF THE STEM OF LYCOPODIUM. 3l 
it may be stated that, with regard to sieve-tubes, they were found to be very similar to 
the sieve-tubes of other Pteridophyta. It is almost impossible to detect them in sections 
mounted in balsam, and for this reason microtome-sections could not generally be used 
for their examination. Stained with chlor-zinc-iodine, or better with Russow’s solution, 
they showed up very clearly, and resemble perhaps most nearly the sieve-tubes of Pinus, 
having sieve-areas and sieve-plates (figs. 56, 57). With the magnifications used, and 
without undertaking a long series of investigations with special stains, it does not seem 
to be possible to determine whether callus is present, although it may be expected. The 
sieve-tubes are very long and end-walls very rare, but they appear to be transverse or 
slightly oblique and are quite thin. It will be noted that the structure of the sieve- 
plates is not correctly represented in the figure given in Janezewski's paper (9). 
'The endodermal layers of several species, and taken at different points, were examined 
to see whether the development of the cuticular bands could be followed out. In the 
species for which a single layer of endodermis has been previously recorded, L. Selago 
and inwndatum, the early formation of a cuticular thickening on the radial walls, or on 
radial and external walls simultaneously, was observed, but it does not appear all round 
the stem at the same time. This unequal development is a distinet feature of 
Lycopodium, both as regards the endodermis and the thickening of the cortex. In other 
cases, even although the stems were in an early stage of differentiation, cuticularisation 
appeared to be produced simultaneously on the walls of two layers of cells. 
The formation of spiral thickenings in the inner cortical cells of a specimen of 
L. complanatum has been already mentioned, and beyond that no spiral tracheids were 
found outside the true xylem. "The appearance of spiral markings seen in cortical cells 
in transverse sections was always found to be due to pits. 
The proportion of phloem to xylem has been variously estimated: in the stems of 
such species as Z. clavatum and complanatum, where the phloem-bands are narrow, the 
proportion of phloem does not appear to be less than in the stem of most Ferns, while the 
area of the phloem in the section of the stem of L. alpinum shown (Pl. 4. fig. 15) is 
proportionately greater; the stem of L. squarrosum shows a maximum amount of 
phloem, while in the other epiphytic Lycopods examined there is proportionally less with 
a minimum in the case of L. cernuum. In the branches the proportion of phloem 
decreases. The most obvious explanation is to correlate the amount of phloem with the 
needs of the plant for storage-accommodation, since the phloem contains so much proteid 
material, and this would be in keeping with the large amount of phloem found in the 
stem of the epiphytic species. 
ANATOMY AND CLASSIFICATION. 
It is interesting to see how far the results of anatomical investigation are in accord 
with the classification adopted by systematists. It will be evident that the twenty 
species mentioned in this paper have been separated into two groups, the second 
containing a number of epiphytic forms and the first plants with horizontally 
growing stems, while species with erect stems may be included in either group, 
SECOND SERIES.— BOTANY, VOL. VII. G 
