958 PROFESSOR W. C. WILLIAMSON AND DR. D. H. SCOTT ON THE 
Fig. 48. Part of the transverse section of the largest stem, showing secondary wood, 
x; cambium, cb; phloém, ph; and internal periderm, pd. C.N. 914. x 50. 
Fig. 49. Part of the secondary wood of the same specimen, in radial section; 1, 
medullary rays. C.N. 924. x 100. 
Fig. 50. Part of the secondary wood of a large stem, in tangential section, showing 
the medullary rays (7), of various heights, and the scalariform pits of the 
trachez ; compare with fig. 47B. C.N. 921. x 100. 
Fig. 51. Part of a transverse section of the largest stem. *, secondary wood ; cb, 
cambium ; ph, phloém ; pd, inner layers of periderm. C.N. 913. x 100. 
Fig. 52. Corresponding radial section from the same specimen; lettering as before. 
Note the elements in the phloém resembling sieve-tubes. 
The separation between periderm and phloém is accidental; in other parts 
of the section they are continuous. The delicate layer which is severed is 
probably phellogen. C.N. 924. x 100. 
PLATE 85. 
Fig. 53. Sphenophyllum insigne. Part of a longitudinal section of the wood, passing 
through the canal, and showing the spiral tracheze of the protoxylem, pa. 
To the left of the canal is primary xylem, x; to the right the secondary 
wood, x”, begins. The section is somewhat oblique. 
From a stem of moderate size, with secondary wood 7-9 cells thick. O.N. 
922. X 100. 
Figs. 54-58. Sphenophyllum Dawson. 
Fig. 54. Part of a longitudinal section of a small strobilus, showing 4 whorls of 
bracts. The section is partly radial, partly tangential. «, part of xylem of 
axis ; sp, various sporangiophores, showing attachment to bracts. F ragments 
of sporangia, and numerous spores, are shown. C.N. 1898K. x 15. 
Fig. 55. Part of a transverse section, through the whorl of bracts close to its 
insertion on the axis. From the section figured by Winutamson, “ Organiza- 
tion,” Part XVIII., Plate 27, fig. 9. Three bundles are shown just separating 
from one another. 0., bundle going to a bract; sp, sp, bundles going to two 
sporangiophores. C.N. 10494. x 200. 
Fig. 56. Corresponding section from the same specimen, taken through the whorl of 
bracts, a little higher up than the last. From the section figured by 
WILLIAMSON, loc, cit., Part XVIIL, Plate 26, fig. 2. The three bundles have 
now quite separated, and the projecting bases of the sporangiophores are seen. 
6, bundle going to bract; sp, sp, bases of sporangiophores. C.N. 10498, 
x 100. 
