208 DR. D. H. SCOTT : 
wood abuts on the tissue separating the two strands and appears to belong 
to neither : ultimately, however, this also is divided between them. 
Two sections further up (section 17, Phot. 9) the two strands are com- 
pletely organized as separate bundles, each with its own are of secondary 
wood ; the rows of the wood spring from both flanks of either strand, and 
are beginning to extend further inwards. The protoxylem-groups are here 
over 3 mm. apart, the clear distance between the two primary strands being 
nearly 2°5 mm. A wide ray is appearing between the two fans of secondary 
wood. 
In the next two sections rows of secondary wood appear between the two 
bundles of the trace, and in the bundles themselves the secondary growth 
begins to extend to the inner, adaxial side. Lastly, in the uppermost section 
of the series (section 20, Phot. 10) there is a considerable tract of secondary 
wood between the two strands extending far to the inside. It is also closing 
in directly behind the right-hand (upper) bundle. In this strand the 
secondary wood proper to the strand now clearly extends all round, the rows 
on the adaxial side still being short. In the left-hand (lower) strand the 
adaxial wood is less evident, but this may be merely a matter of preservation. 
The right-hand bundle lies beyond the limits of the adjacent secondary wood, 
while that on the left appears to be less far out. 
In each bundle the primary xylem is radially elongated, an appearance 
no doubt due in some degree to the oblique course of the outgoing trace. 
The protoxylem, here as in the original single strand, lies somewhat nearer the 
outer than the inner edge: it may be beginning to divide, but this is doubtful. 
The section last, described comes next below that already figured in the 
Kentucky paper (Scott & Jeffrey, 1914, Pl. 29. Phot. 22 ; Pl. 30. Phot. 28). 
This section is reversed as compared with those of the new series; the 
complete bundle shown in the former corresponds to the left-hand (lower) 
strand in the photographs now given. The chief changes are that the 
secondary wood of the stele has at the higher level completely closed in 
behind this strand and the strand itself has well-developed wood all round it, 
as deseribed in the Kentucky paper (p. 324). The compauion strand (the 
right-hand (upper) one in the new series, left-hand in the 1914 figure) is 
only represented by a fragment in the old section. 
The series just described demonstrates, with perfect clearness, the division 
of the leaf-trace into two equivalent strands as it passes out through the 
secondary wood. The latter, however, is a late formation, and a better way 
of expressing the facts is to say that the trace divided before reaching the 
pericycle : i.e., while still within the zone of thickening. In this it differs 
from the leaf-trace of C. Saturni, which, according to the detailed observa- 
tions of Solms-Laubach, passed beyond the woody zone as a single bundle, 
and only divided into two in the cortex (Solms, 1896, pp. 67, 69; Taf. 4. 
figs. 1-3). The difference, however, is not very great.  Solms-Laubach 
