Botryopteris anti qua, Kids ton. 1047 
stems vary very considerably in size. Thus the sporange photographed in 
Fig. 18 is nearly double the size of any member of the group of four in 
Fig. 17. The latter show the same dimensions (275 fj.) and arrangement 
as those described recently by Dr. Scott. 1 
The specimens considered occur in three different blocks of calcite, 
but in spite of all the range of variation they exhibit, it has not been found 
possible to demonstrate the presence of more than one species. 
III. Node and Internode. 
In that part of the stem which is not complicated by the emission of 
roots, the structure of the stele throughout the node and internode is 
characterized by a very simple series of changes. As the leaf-trace 
separates from the stem xylem, the latter consists of a mass of primary 
tracheides with but one protoxylem group placed laterally very near the 
surface of separation of the trace (PI. LXXXI, Fig. 1). In cases where 
the leaf-trace is equal in size to the stem stele there is little to distinguish 
the trace from the stele (cp. Figs. 7 and 8 a). The trace separates off along 
one margin first, and gradually increases its angular divergence until it lies 
at 90° to its plane of attachment (PI. LXXXII, Figs. 11 and 12). 
The protoxylem group left in the stem bifurcates, and after a very 
short interval (within three millimetres sometimes) two protoxylem groups 
are to be seen, now surrounded by metaxylem. Photographs of stem 
sections in this plane are shown in Figs. 2, 8 a, and 9 a. These are each 
from a different specimen and agree in demonstrating the formation of 
peripheral metaxylem elements which restores the mesarch position of the 
two protoxylem groups. One of these groups is the new leaf-trace group, 
which is thus clearly shown to be mesarch in origin. 
IV. The Leaf-trace and Petiolar Bundle. 
One of the two above-mentioned protoxylem groups, lying at two-fifth 
angular divergence from the point of departure of the last leaf-trace, may 
now be looked upon as destined for the next leaf. As already stated, it 
may pass out undivided, in which case we have a monarch trace and 
monarch petiolar bundle (PI. LXXXI, Figs. 4 a and 9; PI. LXXXII, 
Fig. 14; PI. LXXXIII, Figs. 19 and 21). 
Very frequently in the specimens under consideration the protoxylem 
of the leaf-trace is duplicated (Fig. 11) while still in contact with the 
stem xylem. An early stage in this duplication is indicated in Fig. 6 a, 
where separation is 11 just being initiated. While the leaf-trace is passing 
through the cortex of the stem, all formation of strictly centrifugal meta¬ 
xylem ceases, but the protoxylems line the bottom of adaxial grooves 
owing to the differentiation of elements of metaxylem laterally. These 
1 Scott: Sporangia attributed to B. antiqua, Kidston. Annals of Botany, 1910, Note, p. 820. 
