30 MR. C. E. JONES ON THE MORPHOLOGY 
As a type of monopodial branching, figures of L. clavatum are given (PI. 5. figs. 44— 
49). In this case the branches arise laterally and the vascular elements broaden out in 
the vertical plane. Eventually, in several of the xylem-bands towards the side where 
the branch will come off, the xylem-elements become smaller, and at this point the 
separation will occur between the stem and branch portions of the vascular elements. 
It will be observed (fig. 45) that four or five bands of xylem, together with the included 
phloems, give off connections to the branch: the number varies with the size of the 
branch. The protoxylems together with metaxylem then separate off, the result being 
that on the adjacent sides of stem and branch protoxylems are wanting. Very shortly, 
however (fig. 50), protoxylems become evident at these points. It was found by 
examining a branch-origin near the apex that after the branch is cut off, about the stage 
represented in fig. 48, the meristem begins to form protoxylem in addition to the 
metaxylem, at the point where protoxylems normally occur. There is, therefore, a break 
in the continuity of the protoxylem. 
The connection of the root is practically similar to the connection of a branch, but the 
roots run off horizontally, while the vascular cylinders of the branches pass off at a small 
angle. 
The connection of the vascular cylinder between the two branches of a dichotomy is 
formed in a similar way (Pl. 5. figs. 51-54). Before the dichotomy occurs the tissues 
broaden out in the plane of separation (figs. 51 & 52). Smaller xylem-elements are 
produced at the centre of the xylem-strands, and at these points separation takes place. 
Tn some sections there appeared to be evidence that before the xylems separate pericycle- 
elements are developed along the centre line, as if the pericycle were pushing into the 
centre of the cylinder (fig. 35). But in other cases if the first elements formed between 
the xylem are considered to be pericyclic, then they have for a time no connection with 
the normal pericyclic ring of cells, Certainly these central elements resemble pericycle 
rather than phloem, but it is not pos 
Then with regard to the formation of 
pre-existing protoxylem-elements, or in some cases a patch of xylem consisting mainly 
is found on the line of division at the periphery on 
parated, these divide into two and pass inwards, 
connecting on to the proximal ends of the bands where protoxylems are wanting. Since 
dichotomies do not occur in most cases, except in the smaller branches, the connection 
between the branches generally consists of not more than two xylem-bands. The figures 
represent a dichotomy in Z. complanatum, a species in which this form of branching is 
very frequent below the strobili. It will be noticeable that with neither of these forms 
of branehing do gaps occur, except with regard to protoxylems. 
The structure of the leaf-trace, as it 
cortex, is indicated in fig. 58, 
them are thin-walled cells hay 
a ring of endodermal cells, 
Turning to some histological details which have not been satisfactorily 
passes off from the vascular cylinder through the 
The xylem-elements in the centre are well marked ; around 
Ing the appearance of pericycle, and outside may be traced 
established, 
