98 MICROSCOPICAL RESEARCH 



PLATE XIV. 



LEAF STEITCTUEE. 



Fig. 49. Transverse section. Leaf Bud of Sycamore. 'Acerpseudo- 

 platanus ' X 25 dia. (Celloidinised preparation). Stained 

 Borax Carmine. 1. Imbricate bud scales. 2. Developing 

 leaf ' outlined.' 3. Tlie midrib. 4. Lateral veins of leaf. 



Fig. 50. Longitudinal median section of lateral branch of Sycamore, 

 passing through Leaf Stalk of current year ajid Developing 

 Bud of next year x 16 dia. Fixed in 92% Alcohol. Left 

 half only of the section is shown. 1. Pith. 2. Xylem elements 

 of branch. 3. Cambium. 4. Phloem. 5. Cortical tissue. 

 6. Central axis of developing branch. 7. Zone of meristem 

 tissue. 8. Bud scales. 9. Leaves in development. 10. Xylem 

 of developing branch. 11. Petiole of leaf. 12. Ground 

 tissue of SEume. 13. The vascular system. 14. The separating 

 or absciss layer,' which forms during the period of vegetation, 

 and through which ' defoliation ' takes place in Autumn 

 (leaf -fall). 



Fig. 51. Longitudinal mediaji section of a complete Branch of 

 Sycamore, showing the position of the opposite petioles of 

 the current year and the axillary buds for next year's 

 vegetative period. 1. Central axis (pith). 2. Petiole of 

 current year. 3. Central axis of next year's branch. 

 4. Separating layer. 5. Vasculao' bundle leading to leaf. 

 6. Xylem elements of branch. 7. Cambium. 8. Phloem. 

 8a. Cortical tissue. 9. Bud Scales. 10. Developing leaves. 

 11. Growing point of branch. The action of separation 

 has taken place from the point marked X. 



