Maslen . — The Structure of Mesoxylon Sutcliffii (Scott). 413 
EXPLANATION OF PLATES XXXIII-XXXVI. 
Illustrating Mr. A. J. Maslen ’s paper on Mesoxylon Sutcliffii. 
PLATE XXXIII. 
Fig. 1. Transverse section of stem, showing the large pith, the ring of wood and phloem, the 
cortex with attached leaf-bases, and two axillary buds. c.p., central pith ', p.p., peripheral pith; 
l.t., l.t., & c., paired leaf-trace bundles at the margin of the pith (in some of these the two bundles 
are widely separated, in others they are closely approximated, and in yet others the two have fused 
laterally into one bundle ) ; s.x., ring of secondary xylem ; p., phloem ; pe ., pericycle; I'.t'., &c., leaf- 
traces in the phloem and pericycle; d ., Dictyoxylon outer cortex; pm., periderms; l.b., leaf-bases, 
of which seven are seen completely enclosing the stem ; a.b., a.b., axillary buds, one of which is 
accompanied by the subtending leaf-base ; a.b.s., axillary bud-stele in the cortex ; s., space in 
secondary xylem. Slide No. 2621 (S). 1 Magnification just over 3 diameters. 
Fig. 2. Radial longitudinal section of stem, showing discoid pith, &c. c.p ., central discoid 
pith; p.p., p.p., peripheral pith; l.t., leaf-trace bundle at margin of pith; s.x., secondary xylem 
with a central space due to disappearance of the tissue by disorganization (on the right-hand side of 
the section nearly the whole of the wood has been destroyed); p., phloem; pe., pericycle; I'.t'., 
leaf-trace bundle passing into leaf-base ; d., strengthening bands of Dictyoxylon outer cortex ; l.b., 
l.b., leaf-bases; a.b., a.b., leaves belonging to axillary buds; a.b.s., bud-stele in the phloem or 
pericycle ; a., position of abscission layer at base of petiole. Slide No. 2668 (S). Magnification 
4 diameters. 
Fig. 3. Transverse section of a leaf-trace at the margin of the pith with the two bundles widely 
separated, s.b., centrifugal xylem of the bundles; p.b., centripetal xylem of the bundles;/.*., 
position of protoxylem ; s.x., secondary xylem between the bundles; s., space formerly occupied by 
delicate conjunctive parenchyma; p' ., empty thin-walled cells of outer pith; p" ., thicker walled 
cells of outer pith with contents. Slide No. 2634 (S). Magnification nearly 40 diameters. 
Fig. 4. Transverse section of a leaf-trace at the margin of the pith with the two bundles closely 
approximated. Reference letters as in Fig. 3 ; also pa., delicate parenchyma between centripetal 
and centrifugal xylem of bundles; p’" outer pith cells with very dark contents; p'"' ., small empty- 
looking cells of outer pith next the xylem. Slide No. 2653 (S). Magnification about 40 diameters. 
Fig. 5. Transverse section of a leaf-trace at the margin of the pith with the centrifugal xylem 
of the two bundles fused laterally into one, although the two masses of centripetal xylem are still 
separate, s.b., centrifugal xylem; p.b., centripetal xylem; m.r., wide medullary rays in centrifugal 
xylem of bundles; m'.r'., narrow medullary rays in secondary xylem beyond the bundles; outer 
pith cells with very dark contents. Slide No. 2636 (S). Magnification about 40 diameters. 
Fig. 6. Longitudinal section passing through the two bundles of a leaf-trace at the margin of 
the pith, l.t., l.t., leaf-trace bundles; p.b., denser centripetal xylem of bundle; s.b., less compact 
centrifugal xylem of bundle consisting of undulating tracheides separated by relatively broad 
medullary rays ; s.x., secondary xylem of stem consisting in the outer part, a, of closely packed 
straight tracheides with narrow medullary rays, and in the inner part, b, of more loosely arranged 
elements with broader medullary rays; empty cells of outer pith; p" ., cells with contents of 
outer pith. Slide No. 2667 (S). Magnification 20 diameters. 
Fig. 7. Transverse section of outer part of secondary xylem, phloem, and pericycle. s.x., 
secondary xylem; p., phloem; pe., pericycle; p' ., square cells of phloem with very dark contents ; 
p"., cells with paler contents ; p'" ., dark cells at outer limit of phloem ; i.c., cells of inner part of 
cortex. Slide No. 2637 (S). Magnification about 40 diameters. 
PLATE XXXIV. 
Fig. 8. Transverse section, showing a leaf-trace in the inner part of the pericycle. The xylem 
portions of the bundles have already divided, s.b., centrifugal xylem of leaf-trace bundles; p.b. t 
centripetal xylem of leaf-trace bundles ; ph.b., phloem of bundles still undivided ; c., cells with dark 
1 The letter (S) following "the slide number signifies that the sections are in Dr. D. H. Scott’s 
collection. 
