EXPLANATION OF THE FIGURES. 469 



FIG. 



4. Apical view of the terminal bud of Aspidium spinulosum, surrounded by the 



rudiments of the youngest fronds, X 250. 



5. Diagrammatic representation of three divisions of the apical-cell of Aspidium 



filix-mas or spinulosum, and of the displacement caused by the change of 

 form of the apical-cell (see p. 239). The original position of the older 

 walls is shown by dotted lines, the later ones by continuous lines ; both 

 are indicated by the same (Arabic) figures. The Roman figures refer to 

 the cells of the second degree ; II is the oldest, III the intermediate, 

 IV the youngest, of the latter cells. 



C. Diagram of the displacements caused by the next three divisions following 

 the same rule. 



7, 8. Stages of development of the scales of Nephrolepis splendens. 



9 13. The same in Niphobolus rupestris. 



PLATE XXXIII. 



Figs. 1 6. Aspidium filix-femina. 



1. A frond which has been torn off, and kept for a long time in a close, warm 



place, and which has produced an adventitious bud at its base. Natural 

 size. 



2. Longitudinal section of a terminal bud, x 250. 



3. The apex of the lamina of a half-developed frond seen from above, X 250. 



4. Longitudinal section of a young frond, with the rudiment of a root, x 300. 



5. The same somewhat more advanced, x 100. 



6. Longitudinal section of the apex of a root which has not yet broken 



through the tissue of the frond, X 250. 



7. Longitudinal section of the upper end of the frond of Struthiopteris ger- 



manica, x 30. On the developed frond, to the left, is seen the rudiment 

 of an adventitious root. 



8. The last-mentioned rudiment, x 150. 



Figs. 9 20. Maraflia circut(efolia. 



9. Longitudinal section of the end of a stem, x 10. The small circles dis- 

 tributed through the parenchyma are gum-passages. An adventitious root 

 lies deep down in the cortical tissue. Of the youngest of the two visi- 

 ble fronds there is only a small fragment at the side remaining, to which 

 the corresponding membranous lateral portion of the stipule is at- 

 tached. 



10. Longitudinal section of an adventitious bud of the base of the stipule, 



X 30. 



11, 12. Young fronds of different ages seen from above, x 10. 



13, 14. Somewhat older fronds, in longitudinal section, x 10. 



15. Lateral segment of the same, showing a stipule in process of develop- 

 ment, x 10. 



