SHOWING STRUCTURE, FROM THE RHYNIE CHERT BED, ABERDEENSHIRE. 
853 
EXPLANATION OF PLATES. 
(We are indebted to Mr J. Barrie Robinson for re-drawing our reconstructions of the vascular plants 
reproduced on Plates I and II. All the figures on Plates III, IV, and V are from untouched photographs.) 
Plate I. 
Fig. 1. Restoration of Rliynia Gwynne-Vaughani. 
Fig. 2. Restoration of Rliynia major. 
Plate II. 
Fig. 3. Restoration of Hornea Lignieri. 
Fig. 4. Restoration of Asteroxylon Mackiei. 
Plate III. 
Fig. 5. Vertical section of a typical hemispherical projection from a longitudinal section of a stem of 
Rliynia Gwynne-Vaughani. x 100. (No. 2514.) 
Fig. 6. Tangential section of stem of Rhynia Gwynne-Vaughani bearing two hemispherical projections, 
while another has been isolated by the section from the same stem and is seen on the extreme right. x 30. 
(No. 2514.) 
Fig. 7. Portion of specimen in fig. 6 showing the position of the stomata in relation to the two attached 
projections, s., stoma. x 60. (No. 2514.) 
Fig. 8. The detached projection in fig. 6 showing the stoma (s.) with its two guard-cells, x 60. 
(No. 2514.) 
Fig. 9. Small hemispherical projection forming beneath a stoma ( s .). From a tangential section of the 
stem of Rhynia Gwynne-Vaughani. x 200. (No. 2423.) 
Fig. 10. Hemispherical projection on a stem of Rhynia Gwynne-Vaughani , elongated to form a cylindrical 
emergence, x 24. (No. 2515.) 
Fig. 11. Longitudinal section of a stem of Rhynia Givynne-Vaughani showing a hemispherical projection 
on the right, and on the left two necrosed areas, x 14. (No. 2516.) 
Fig. 12. Necrosis cavity from a longitudinal section of the stem of Rhynia Gwynne-Vaughani. The 
cavity is still roofed over by the cuticle and is bounded by cells that have undergone enlargement and cell- 
division. x 50. (No. 2414.) 
Fig. 13. Transverse section of stem of Rhynia Gwynne-Vaughani showing a necrosis cavity and the 
.enlargement and division of the cells around this. x 38. (No. 2406.) 
Fig, 14. Oblique section of stem of Rhynia Givynne-Vaughani showing a large necrosis cavity, the cells 
around which are proliferating. x 36. (No. 2517.) 
Plate IV. 
Fig. 15. Portion of fig. 14 more highly magnified, showing the proliferating cells in the neighbourhood 
of the xylem. x 100. (No. 2517.) 
Fig. 16. Stem of Rhynia Gwynne-Vaughani with vertically elongated and dividing cells bordering on a 
necrosed area, x 50. (No. 2427.) 
Fig. 17. Longitudinal section of tip of stem of Rhynia major, x 28. (No. 2518.) 
Fig. 18. Apex from fig. 17 more highly magnified showing the gradual enlargement of cells behind the 
apical meristem. x 65. (No. 2518.) 
Fig. 19. Two stems of Rhynia major in transverse section. The stem on the right shows a dark necrosed 
area and in relation to this callus-like disturbance and proliferation of the tissues. The stem on the left 
shows a large cavity and similar pathological changes in the tissues. x 15. (No. 2519.) 
Fig. 20. Portion of the wound-tissue from the stem on the left in Fig. 19. x 100. (No. 2519.) 
Fig. 21. Portion of the wound-tissue from the stem on the right in Fig. 19. x 100. (No. 2519.) 
