ON THE STRUCTURE AND AFFINITIES OF METACLEPSYDROPSIS DUPLEX. 175 
and 10) little change can be noticed. One group has come to lie close to the margin 
of the stem xylem, while the other is at the outer extremity of the arm of parenchyma 
and small tracheides. When the level of fig. 9 is reached, however, the second arm 
has disappeared, and at that end of the stem xylem there are two sunk protoxylem 
groups. At the same time the whole end of the stem has a distinct bulge on it. One 
section higher up (fig. 8) the bulge on the stem is still more pronounced; indeed, the 
petiole-trace has now become a distinct body connected to the stem at J by a number 
of very large tracheides. The protoxylem groups are placed at opposite foci of the 
elliptical trace. 
In the section above that shown in fig. 8 the trace has separated from the stem 
as an elliptical mass (fig. 7). This trace was followed outwards for three sections, but 
no change was noted, and above that level it had disappeared. The subsequent changes 
in the petiole-trace will be followed in another series which starts with a much-crushed 
section just about the level shown in Pl. I. fig. 8. Below this level both stem and 
petiole have rotted away. ‘The first section of this new series which is figured, is shown 
in Pl. If]. fig. 34. Here the much-distorted petiole-trace is closely adpressed to the 
stem xylem, and only one protoxylem group can be seen. This group is quite similar 
in position and shape to either of those in Pl. I fig. 7. A few sections higher up, 
however, each protoxylem group has divided into two (PI. IIL. fig. 33, pra), and an 
island of parenchyma is developed at each end, separating the two parts into which 
each protoxylem group has divided (fig. 33, 7s). Fig. 32 represents the highest section 
in this same series, and at the top of the trace there is a mere filament of xylem tissue 
on the outer margin of the island of parenchyma. A closely similar specimen is 
represented by PI. III. fig. 31, where one end of the trace is open while the filament 
is just leaving the other end, ‘There has been some slight lateral crushing in this 
Specimen, as is indicated by the flattened cortex, but it has not affected the trace 
very much. 
In Pl. Ill. fig. 29, however, a similar trace is shown, but in this case there 
appears to have been no distortion. The left-hand end of the trace is open, and shows 
the bay g with the protoxylem elements at each side. The other end is closed and, 
there also, the two groups of protoxylem are clearly seen. So far no distinct pinna- 
trace-bar has been detached from the petiole-trace; though the filaments no doubt 
represent very reduced examples of such departures. The trace shown. in Pl. III. 
fig. 28, while practically identical in form with that of fig. 29, is slightly larger, and on 
the left-hand end the filament of xylem of fig. 29 is represented by a stouter bar. 
Unfortunately these petioles were only short fragments, generally less than half an inch 
long, so that the pinna-trace-bars could not be followed very far. In one example, 
however, from which about twenty sections were prepared, two of these bars were 
followed a short distance, but they never, as far as could be seen, passed out into distinct 
pinne. Though these figures are taken from different specimens, it will be noticed that 
| as the trace increases in size the pinna-trace-bar becomes more and more robust. 
