214 Wiggles worth . — The young Sporophytes of 
Many sections show a few small, apparently protoxylem elements on the 
outer side of the middle of the bows of xylem elements (see px , PI. XXII, 
Fig. 3), but much variation exists with regard to the position of these 
elements. In only one case was the differentiation of the xylem traced 
in the apical region of a root which showed this two-grouped arrangement 
of xylem ; here xylem elements first appeared at three points, but very 
soon a row of small elements united two, and the third was extended 
by the formation of more protoxylem (px, PI. XXII, Fig. 4) into another 
row, separated from the former by thin-walled elements, some of which, by 
their larger size and absence of contents, indicate the formation of metaxylem 
elements ( mx , Fig. 4). This arrangement appears to be distinctly diarch. 
In a rather older sporophyte (Fig. 2) the main root, a little way 
behind the apex, shows a similar structure to that described above, except 
that the two xylem groups have united at one end to form a crescent- 
shaped mass enclosing a central phloem group (PI. XXII, Fig. 5). The 
point of union of the two xylem masses is marked by a group of small 
elements. From this group, a little nearer the base of the root, a some- 
what smaller branch passes off to a rootlet, which, though slighter, appears 
to have originated by dichotomy, and receives a somewhat crescent-shaped 
mass of xylem (see Fig. 6). Lower down the crescent-shaped mass of 
xylem in the main root divides again into two groups separated by 
phloem, and closely resembling the arrangement shown in Fig. 3. It does 
not seem necessary for these two xylem masses to unite before giving off 
a branch to a rootlet, as the tracheides may sometimes be seen coming off 
from one, only, of the xylem masses (see PI. XXII, Figs. 7 and 8), and 
sometimes from the two separate groups ; in the last case the two smaller 
groups of xylem which pass into the smaller branch may unite immediately 
to form a single group. 
It will be observed that the branching of the root has been described 
as dichotomy above. Van Tieghem and Douliot consider that in Lycopodium 
the branches arise immediately behind the apex, but Bruchmann *, who has 
studied the branching of the roots in detail, finds that a pure or modified 
form of dichotomy takes place in the roots of the Lycopodiaceae. He 
figures longitudinal sections through apices of roots of L. complanatum 
showing dichotomy. 
A number of sections made through the roots of L. complanatum and 
L. clavatum supported the view that a modified form of dichotomy 
occurred. It appears that at first one branch of the dichotomy is only 
slightly developed, while the other continues to bore its way straight down 
into the soil ; gradually, however, the branches get more and more equal, 
until finally two equal branches occur. These branches appear irregularly 
arranged on all sides, and they in their turn branch again in a similar manner. 
1 Bruchmann, loc. cit., pp. 73 and 74, Figs. 32, 33, 34, Taf. V. 
