528 
PROFESSOR TV. C. WILLIAMSON ON THE ORGANIZATION 
Fig. 21. An oblique, semi-longitudinal section of the central part of fig. 20. (Refer¬ 
ence letters as in that figure.) 
Fig. 22. Similar section to fig. 20, but from a specimen containing no tylose. (Refer¬ 
ence letters as in that figure.) 
PLATE 17. 
Fig. 23. A divergent vascular bundle passing off laterally through the middle 
cortical layer of a part of the section, fig. 21. Enlarged 62 diameters. 
PLATE 16. 
Fig. 23a. A transverse section of a petiole of Rachiopteris robusta. Enlarged 30 
diameters. 
PLATE 17. 
Cryptogamic Reproductive Organs. 
Fig. 24. Transverse section through a matured capsule of Sporocarpon elegans in 
its matured state. Enlarged 93 diameters, a. Hour-glass bases of 
unicellular hairs, b. Peripheral extensions of a. c. Bases of hairs inter¬ 
mediate between the states a and c. d. Spaces between the hour-glass 
cells, a, and occupied by an intermediate layer of cells. 
Fig. 25. Tangential section of a crushed example like fig. 24, the cells being 
intersected radially at a, and transversely at c where their outer 
extremities are exposed. The interior is occupied by a cluster of large 
cells. Enlarged 93 diameters. 
Fig. 26. A yet more tangential section of a Sporocarpon elegans displaying the 
symmetrically disposed, outer ends of the cells at its peripheral surface, 
and passing obliquely into the internal cavity of the organism at the 
interior of the section. Enlarged 93 diameters. 
Fig. 27. Similar section to fig. 26, but yet more peripheral. Enlarged 93 diameters. 
Fig. 28. Oblique section through a part of the cellular-wall of Sporocarpon elegans. 
a. Its inner surface formed of the expanded centripetal extremities of 
the hour-glass cells, b. The inner portions of the constricted parts of 
the same cells, c. The outer expanded portions of these cells, d. The 
free portions of the cells prolonged into hairs, e, e'. Delicate cell-walls 
of cells forming the central layer, and connecting the hour-glass con¬ 
stricted cells. Enlarged 320 diameters. 
Fig. 29. A superficial tangential section of the object designated Sporocarpon 
compactum in the memoir, Part IX. Enlarged 93 diameters. 
