AND ANATOMY OF THE STEM OF LYCOPODIUM. 29 
phloem of the vascular cylinder of the stem. In most cases the extensions of xylem 
passing off join up behind as the root-trace separates, with the result that a crescent- 
shaped mass of xylem is formed with protoxylems at the horns of the cresceat, and the 
bay is occupied with phloem. In fewer cases the xylems do not join up, and then, as 
in branches, jour protoxylems often may be detected. The roots all have a similar 
orientation, even where several are found, and relatively they change their position but 
little; the horns of the crescent are always turned outwards. With regard to the length 
of these roots, which do not emerge from the stem, they have been found to run down 
for distances varying from 1 em. to 2:3 cm. 
Aprx.—Except in the early paper by Nägeli (1), describing the structure in the root- 
apex of L. clavatum, the evidence has been entirely opposed to the existence of a single 
apical cell in Lycopods, and this decision may be accepted ; but Strasburger ( 7) and, less 
definitely, Hegelmaier (5) have pointed out that in longitudinal sections of the stem a 
deeper cell is generally found at the apex, and Strasburger traced out the development of 
dermatogen and periblem from one outer cell and the development of the phloem from 
one or two inner cells. The writer has obtained results on the whole very similar to 
those of Strasburger, but it is not proposed to enter into the discussion of the apex 
and the differentiation of tissues. The photograph of a narrow apex of the stem 
of L. inundatum shows the divisions very clearly, and has therefore been reproduced 
(Pl.3.fig. 7). The deeper cell at the apex has divided into two by a longitudinal division, 
and the cell below has undergone transverse division; the plerome and periblem can 
also be demarcated. 
Brancuine.—It is generally stated that in Lycopods the branching of the stem 
is always monopodial, although it sometimes simulates a dichotomy. The opposite 
view has also been put forward that the branching is normally a dichotomy, and that 
monopodial branching is due to the retardation or cessation of growth of one axis. There 
is, again, the question whether dichotomy is to be limited to those cases where a true 
apical cell is found and where the two branches arise from the two halves of the apical 
cell. In Pritzel’s account of Lycopodium (13) the statement appears that the growing- 
point ceases to form new tissue and two new lateral growing-points are developed ; but 
the evidence upon which this opinion is based is not given. I am inclined to regard 
these definitions as too extreme, and in the case where no definite cell exists, then the 
formation of two similar apices, either traceable in the young condition or based upon the 
evidence of subsequent similar development of the tissues, may be termed a dichotomy. 
In L. complanatum it is possible to recognise, shortly before the strobili are formed, not 
only on that part of the piant which will form the strobilus but also on adjacent 
sterile shoots, branchings which would in this sense be termed dichotomies. Sometimes 
it is possible to recognise them externally, as is generally the case with L. complanatum. 
In the allied form, L. alpinum, they are not so well defined, and it is necessary to cut 
sections through the tassels of branches, when the forking is generally monopodial, but 
occasionally a dichotomy is met with. In the creeping Lycopods monopodial branching 
is found, except in the strobilar region or below it. In epiphytic forms dichotomies are 
probably the rule. 
