Mesoxylon and an Allied Genus . 13 
The other specimen, represented by six sections, is more remarkable, 
for the axis increases rapidly in diameter from below upwards, and appears 
to approach the growing point at the upper end. 1 At the base (section 
3017) the shoot measures altogether about 4*5 mm. in diameter; the stele 
is about i«7 mm., with a minute pith, only about 0*4 mm. in diameter; the 
wood is of unequal thickness, from 0*37 to 0*9 mm. (PI. I, Fig. 9). Two 
single leaf-traces are passing out. The cortex and leaf-bases are obscure 
in this section, but the axis is surrounded by broad, ill-preserved leaves. 
In the next section (3018) the diameter of the shoot has increased to 
7-8 mm. The stele is incomplete, but evidently larger than before, with 
the wood 0-53 mm. thick in the part preserved ; numerous bundles are seen 
entering a leaf-base, as in the previous specimen. The third section (3019) 
(PI. II, Fig. 10) is a much better one and shows a marked change. The 
diameter of the whole shoot is here about 8x10 mm. The stele measures 
3x2-5 mm. and the pith, which is pentagonal in form with gaps at the 
angles, about 1-5 mm. The wood reaches 0-57 mm. (24-30 elements) in 
thickness. A large single leaf-trace is passing out. The pith here, as in 
all the sections which show it, seems continuous; there is nowhere any 
indication of a discoid structure. Centripetal xylem is distinctly shown at 
certain points around the pith. 
In the fourth section (3020) the dimensions have further increased, 
the whole diameter being about iox 15 mm. The stele has a diameter of 
3x2-8 mm. and the pentagonal pith of i-8 mm.; the wood has a fairly 
uniform thickness of 0-4 mm. There is a forking leaf-trace in the cortex, 
opposite one of the gaps in the ring of wood. 
In the two sections last mentioned the large leaf-bases and the 
encircling leaves are better preserved, though still imperfect ; they seem 
to agree essentially with those of the former specimen ; certainly the leaf- 
bases are relatively more strongly developed than on the vegetative stems 
of Mesoxylon , and the leaves themselves are polydesmic and probably of 
the Cordaitean type. 
In the next section of the series (3021) the axis is destroyed, but the 
uppermost section (3022) is interesting, for it shows the stele in a very 
young condition. The preservation is bad on the whole, but a ring of 
quite isolated, vascular bundles is shown. There appear to be nine of these 
bundles, though some are obscure, surrounding a large pith and separated 
by broad principal rays. The secondary wood of each bundle is only four 
or five cells thick ; in some cases a few centripetal elements can be 
recognized. At one place a leaf-trace is passing out, almost horizontally. 
1 The series is 3017-22, from below upwards. The sections were received from Mr. Lomax in 
October, 1910. He rightly regarded this specimen also as an apical shoot (possibly, as he then 
thought, of Mesoxylon multirame) and attached great importance to its intimate association with 
the seeds. 
