144 Johnson. — On the Development of the 
Fig. 5. Dorsal surface of the tip of a similar leaf, x 400. 
Fig. 6. Half of a nearly transverse section of a young leaf showing the shape of 
a segment and the position of the first two section- walls, x 700. 
Fig. 7. The same still older, x 750. 
Fig. 8. Transverse section of petiole in which epidermal and hypodermal layers 
are completed and the partition-cells are nearly ready to cut off the cross-partition - 
cells, x 750. 
Fig. 9. The same section of a still older petiole, x 400. 
Fig. 10. Transverse section of a nearly mature petiole, x 60. 
Fig. 11. Tangential section of petiole showing the air-canals and partitions, 
x 400. 
Fig. 12. The same in a slightly older petiole, x 400. 
Fig. 13. The same still later showing the lengthening of the longitudinal 
partition, x 400. 
Fig. 14. Surface view of a longitudinal partition showing the pores in a nearly 
mature petiole, x 125. 
Fig. 15. Surface view of petiole showing the arrangement of the trichomes. 
x 750. 
Fig. 16. Nearly mature stage of same, x 300. 
Fig. 17. Nearly mature trichome. x 60. 
Fig. 18. Horizontal section of the tip of a leaf, showing the beginning of the first 
pinnae, x 400. 
Fig. 19. Sagittal section of a leaf through one of the well-developed lower 
pinnae, x 400. 
Fig. 20. Transverse section of a leaf through pinnae, a little later than Fig. 18. 
x 300. 
Fig. 21. A similar section still later, x 125. 
Fig. 22. A transverse section of petiole showing origin of sporocarp. x 750. 
Fig 23. Part of an approximately horizontal section of base of a leaf showing 
the apical cell of sporocarp. x 75°* 
Fig. 24. Transverse section of stem, and a young leaf with two sporocarps, all 
three nearly parallel to the stem, x 150. 
Fig. 25. Inner side of a young leaf with a sporocarp in which the segmentation 
of the apical cell is nearly finished, x 25. 
PLATE XI. 
Fig. 26. Nearly horizontal section of a stem through two leaves, an axillary 
branch and two sporocarp-rudiments, showing the under surface of part of older 
leaf, and cross-section of the first sporocarp arising on this ; also the origin of 
a second sporocarp from the first, x 400. 
Fig. 27. Transverse section of a young sporocarp. x 75 °* 
Fig. 28. Transverse section through the basiscopic ultimate marginal cell of a 
sporocarp after all six sections are formed, x 75°- 
Fig. 29. The same section of a capsule at the time of beginning of soral canal, 
showing relative thickness of older and younger walls, x 750. 
Fig- 3°* Part of transverse section of older capsule. x 75°- 
Fig. 31. The same still older, x 400. 
