CYCADOFILICES FROM THE CALCIFEROUS SANDSTONE SERIES. 825 
Fig. 8. Transverse section of part of axis to show structure of wood. x!=primary wood; prz. = proto- 
xylem ; #?=secondary xylem; m7.=medullary rays; w.r,=ring of small tracheides. See also Pl. III. 
fig, 24. Slide 1005. x19. 
Fig. 9. Section similar to fig. 8. a, m.r., w.r. as in that figure. Slide 1006. x19. 
Puate II, 
Rhetinangium arbert. 
Fig. 10. Transverse section of part of stem. 2*=secondary wood; ph.=phloem; 7.c.=inner cortex ; 
e.t,=crushed cells at exterior of inner cortex; 0.c.=outer cortex; s.s,=secretory sacs in inner cortex ; 
s.c.=secretory cells in inner cortex. Slide 1006. x 30. 
Fig. 11. Longitudinal section of inner cortex. Lettering as before. Slide 1077. x 14. 
Fig. 12. Transverse section of root-trace. 2!=primary xylem ; 7?=secondary xylem ; prx. =protoxylem. 
Slide 1037. x 70. 
Fig. 13. Longitudinal section of part of outer cortex. p.o.c.=parenchymatous outer cortex; s¢c.0.c. = 
sclerotic outer cortex ; s.s.=secretory sacs. Slide 986. x 36. 
Fig. 14. Transverse section of part of outer cortex. ¢.0.c.=elongated outer cortex; sc.o.c. =sclerotic 
outer cortex ; s.s.=secretory sacs. Slide 1003. x 36. 
Fig. 15. Transverse section of cortex. %.c.=inner cortex; ¢.0.c.=elongated outer cortex; s¢.o.c.= 
sclerotic outer cortex ; s.s. secretory sacs. Slide 1048. x 23. 
Puate III. 
Rhetinangium arbert and Heterangium grievit. 
Fig. 16. &. arberi. Transverse section of petiole-trace while attached to the axis of the stem, z= 
primary xylem; x?=secondary xylem; pra.=protoxylem of leaf-trace; /.t.=leaf-trace. While transfer- 
ring this section a crack appeared in the specimen, and although the trace is still complete it has parted from 
the rest of the section near one end. Slide 994. x19. 
Fig. 17. R. arbert, Transverse section of petiole-trace at a slightly lower level. «as. =secondary. wood 
of stem ; pra. =protoxylem groups of petiole-trace. Slide 999. x 34. 
Fig. 18. &. arbert. Transverse section of petiole-trace at a still lower level. xs. =secondary wood of 
stem; #?=secondary wood on back of petiole-trace ; pra.=protoxylem groups of petiole-trace. Slide 
1003. x 34. 
Fig. 19. &. arberi. Transverse section of petiole-trace in free petiole. Slide 1048. x 16. 
Fig. 20. R. arberi. Transverse section of trace in smallest observed division of the petiole. U.t.=trace ; 
prx.=some of the protoxylem groups. Slide 1005. x 60. 
Fig. 21. Heterangium grievt. Transverse section of petiole-trace while still joined to central axis of 
stem. (Compare with &. arberi, fig. 16.) /.t.=petiole-trace ; 21=primary xylem of stem ; x?=secondary 
xylem of stem; prx.=protoxylem. Scorr Collection 1016. . x 60. 
Fig. 22. Heterangium grievii. Transverse section of stem. (Compare with R. arbert, Pl. I. fig. 2.) 
Kipston Collection 512. x 8°5. 
Fig. 23. R. arbert. Longitudinal section of outer cortex showing radial elongation and the occasional 
division of the inner cortical parenchyma. p.o.c.=parenchymatous outer cortex ; sc.o.c,.=sclerotic outer 
cortex ; a=radially elongated parenchyma; ¢.w, = wall dividing elongated cells into two. Slide 984. x 36. 
Fig. 24. &. arberi, Transverse section of peripheral primary wood to show position of protoxylem. 
Part of section shown in PI. I. fig. 8. The photographs are reversed in position. w!=primary wood; pra. 
protoxylem ; #?=secondary wood; ¢.p.=conjunctive parenchyma of primary wood; m.7.=medullary ray. 
Slide 1005. x 85. 
Fig. 25. R. arbert. Longitudinal section of primary xylem cylinder to show secretory sacs and cells. 
zi=primary xylem group; ¢.p.=conjunctive parenchyma; s.s.=secretory sacs ; s.c.=secretory cells, Slide 
984. x 45. 
TRANS. ROY. SOC. EDIN., VOL. XLVIII. PART IV. (NO. 29). 120 
