.'^O Puget Sound Marine Sta. Pub. Vol. 1, No. 



PLATE 8 



Fig. 10. Diagram of stipe of a two-year-old plant, showing the 

 annual rings, and the first rifts formed. X3. 



Fig. 11. Diagrammatic cross section of rachis from which sporo- 

 phylls are seen to be sent off; rifts are seen in the pith. X3. 



Fig. 12. Diagrammatic cross section of the midrib of the lower 

 portion of the lamina; pith region shows the extremities being enlarged, 

 foreshadowing separation from the central pith; rifts at center. X3. 



Fig. 13. Diagrammatic cross section of upper midrib of lamina, 

 showing first true chamber; sieve-tube areas are definitely organized. X3. 



Fig. 14. Diagrammatic cross section of mature midrib showing 

 character of the chamber. X2. 



Fig. 15. Diagrammatic cross section of mature midrib, showing the 

 septum. X2. 



Fig. 16. Acutely angled extremity of the same chamber shown 

 in Fig. 13. X53. 



Fig. 17. Strengthened region at part of the chamber where an 

 acute angle had indicated the rending of tissues along median line of 

 pith area. The torn hyphae along the chamber wall have almost wholly 

 disappeared. X53. 



Fig. 18. Longitudinal section of mature midrib, cut perpendicular 

 to the plane of the lamina. XI -5. 



Fig. 19. Longitudinal section of mature midrib, cut parallel to 

 the plane of the lamina. Xl-5. 



Fig. 20. Nearly mature septum; sharp line of demarcation be- 

 tween pith and cortex has disappeared. X53. 



