THE MORPHOLOGY OF THE STELE OF PLATYZOMA MICROPHYLLUM, R. BR. 595 
Fig. 16. Transverse section of the stele at a point in advance of that represented in fig. 15. A medul- 
lated protostele has been established locally. ( x 50.) 
Fig. 17. Transverse section of the stele at a point in advance of that represented in fig. 16. The pith 
has been augmented and within it a new endodermal-formation has arisen. ( x 50.) 
Fig. 18. Transverse section of the stele at a point in advance of that represented in fig. 17. A complete 
inner endodermal tube has been formed, and part of the pith which it includes is sclerotic. ( x 50.) 
Plate III. 
Fig. 19. Transverse section of the stele at a point in advance of that represented in fig. 18. The inner 
endodermal-cylinder has become locally narrow. ( x 50.) 
Fig. 20. Transverse section of the stele at a point in advance of that represented in fig. 19. The inner 
endodermal-cylinder has again expanded. ( x 50.) 
Figs. 21-25. A series of transverse sections of the stele at successive points in advance of that represented 
in fig. 20. Fig. 25 represents the undifferentiated stele just behind the growing apex of the stem, while 
figs. 24, 23, 22, 21 show successive steps in the stelar differentiation. ( x 50.) 
Fig. 26. Transverse section of a portion of the vascular cylinder in a section lent by Dr Scott and 
Mr Boodle. It represents a xylem-ray at the point of departure of a small leaf-trace. ( x 100.) 
Fig. 27. Transverse section of a portion of the stele of Platyzoma to show the spiral protoxylem groups 
seen occasionally in the leaf-trace. ( x 100.) 
TRANS. ROY. SOC. EDIN., VOL. LII, PART III. (NO. 22). 
90 
