Stephenson. — Young Stages of Dicksonia and Cyathea. 15 



Fig. 9. Transverse section, immature petiole, x 250. px., protoxylem ; 

 i.v., young tracheid ; d.l., dense layer of cells surrounding the 

 protoxylem, f-nd growing in to form the cavity parenchyma. 



Fig. 10. Bundle of leaf of Dicksonia, near end of leaflet, x 250. 



Fig. 11. Bundle of leaf of Cyathea dealbata, near end of leaflet, x 250. 



Plates II, III. 



Figs. 12-18. Vertical (microtome) sections of prothallia of Dicksonia 

 squarrosa parallel to longitudinal axis of thallus. The 

 sections show the development of the archegonium. x 250. 



Fig. 19. Sections parallel to surface, showing cells cut off in the paren- 



chyma surrounding the egg cell, x 250. 



Fig. 20. Similar section, showing cuticularisatkn of walls of venter. 



X 250. 



Figs. 21-24. Surface views of young prothallia and their first archegcnia. 

 The shaded cells are the archegonium mother cells (C. 

 medullaris). x 250. 



Figs. 25-29. Transition from stele of root (fig. 25) to just below foot 

 (fig. 27) to protostele of stem (fig. 29). x 250. 



Fig. 30. Transverse section, first rcot C. dealbata. Characteristic 



thickened layer, x 250. 



Fig. 31. Mature root D. squarrosa. c, compressed tissue, x 120. 



Fig. 32. Part mature rcot C. Cunninghamii, showing separated pro- 



toxylem. x 120. 



Figs. 33-36. C. dealbata. Four successive transverse sections near rpex,. 

 showing insertion of protoxylem elements of the petiole 

 ■ T i> x i> on to those of stem s-y-e^. s 3 and s s are connected 

 with next leaf, x 250. 



Figs. 37-41. Transition protostele to siphcnostele in C. Cunninghamii^ 

 between first and second leaves, x 250. 



Fig. 42. Early stage, medullary bundle, C. Cunninghamii. x 250. 



Fig. 43. Solenostele in a Dicksonia, -fa in. long, x 60. 



Fig. 44. Transverse section near apex of runner of D. fibrosa, shewing 



the scalariform irregularly disposed first-formed xylem. 

 X 80. 



Fig. 45. Transverse section, stem, mativre Dicksonia. Trochoids in 



rather regrdar rows, with parenchyma between. Well- 

 defined layer of sieve-tubes, x 60. 



Plate IV. 



Figs. 46, 47. Epidermis developing leaf, C. dealbata and D. squarrosa. 



Fig. 48. Apex leaf, longitudinal section. 



Fig. 49. Stoma, nearly mat me, seen from below. 



Figs. 50-59. Developed prothallia, D. squarrosa. 



Figs. 60-68. Cyathea Cunninghamii. Figs. 60-63, abnormal forms, due to 



overcrowding; figs. 64-68, antheridia en fikmentcus 



protha'lia. 

 Fig. 69. Verticfl section, embryo, with basal and quadrant walls 



darkened, c, apical cell, first leaf ; st., stem quadrant ; 



/., foot quadrant. 

 Fig. 70. Later embryo. Only root and first leaf have grown much. 



Figs. 71, 72. Embryos dissected out and mounted whole. 

 Fig. 73. Dicksonia, six leaves ; longitudinal section, shewing apical 



cell. 

 Fig. 74. Transverse section, similar stage. 



Fig. 75. Transverse section, mature apex of C. dealbata. Segments 



cut off in order (s v s 2 , s 3 ). 



