776 PROFESSOR W. GC. WILLIAMSON AND DR. D. H. SCOTT ON THE 
Fig, 164. From a section of another leaflet, to show a stoma on the lower surface. 
s.t., part of the spongy tissue; ep., epidermis; s.c., prominent subsidiary 
cells; g.c., depressed guard-cells of the stoma. x 500. C.N. 1197 (see 
ps (ol) 
Fig. 17. Transverse section of the same root, rt.*, which in figs. 18 and 184 is seen in 
connection with a stem of Lyginodendron. This is from a third section of 
the specimen, where this root has become free. Note its typical Kaloxylon 
structure. px., px., two of the seven protoxylem-groups ; &., primary wood ; 
x.°, secondary wood; ph., phloém; c.’, inner cortex; ¢., outer cortex, or 
epidermal layer. xX 30. O.N. 18858 (see p. 734). 
PLATE 25. 
Fig. 18. Oblique section of a stem of Lyginodendron, showing roots (= Kaloxylon 
Hooker) in connection with it. t.! and rt.*, two free roots; rt.? and rt.‘, 
two roots in connection with the stem ; 7.x., part of xylem of rt.°, traversing 
cortex of stem; br., rootlet given off by rt.t; rt.5, base of a fifth root, at its 
junction with wood of stem; d.c., Dictyoxylon cortex of stem; x.*, its 
secondary wood; .b., primary xylem-strands. Cf fig. 17. x6. CON. 
1885a (see p. 734). 
Fig. 18a. Another section of the same specimen. All the four roots,7t.'—rt.*, are shown; 
rt and rt.? remain free, rt. and rt.* are here seen in obliquely longitudinal 
section; 7.x., xylem of roots; that of rt.4 can be traced through cortex of 
stem. Lettering as before. x 6. C.N. 1885c (see p. 734). 
Fig. 19. Part of a radial section of a root, to show position of protoxylem. pzx., 
protoxylem ; «., primary xylem; c¢.p., conjunctive parenchyma ; pe., en., 
probable pericycle and endodermis; s.s., secretory sacs in cortex. xX 100. 
C.N. 1633 (see p. 736). 
Fig. 20. Part of a transverse section of a hexarch root, at the commencement of 
secondary growth; px., three of the protoxylem-groups. That to the left 
is connected with the base of a rootlet. «, ., primary xylem; c.p,, 
conjunctive parenchyma; ph., three phloém-groups, alternating with the 
protoxylem; cb., cambium, just beginning its activity opposite the phloém- 
groups ; en., endodermis. x 100. C.N. 1631 (see pp. 736 and 739). 
Plates 26 and 27.—Heterangium Grievii. 
PLATE 26. 
Fig. 21. Transverse section through a young stem giving off a branch, br. pe., peri- 
cycle of main stem, enclosing the stele: /.t., 1.t., leaf-trace bundles; ze, 
