PLATE XXIV. 



1. Segment of distal face of ring, showing tlie seat of the new joint. 



2. The proximal face of the same ring. 



3. A segment of a i-ing in which the radiating ridges have become quite numerous, with the seat of a 



new ring. 



4. Segment of new ring reaching the outer edge. 



5. Profile view of same young ring. 



6. Section across two rings, showing tlie position and shape of a new ring. 



7. A ribbed and a flat ring in the middle part of the stem with a very young ring. 



8. 9, 10. Young rings seen in profile fitting between the older rings, and not yet extending to the outer 



surface. 



11. Oblique view of reticulation round the opening of the axial cord of two adjoining rings. 



12. Outline of reticulation round the axial opening of another ring. 



13. Thickened edge of the opening for the axial cords. 



14. A few of the meshes of the central part of the reticulation greatly enlarged. 



