194 Scientific Proceedings, Royal Duhlin Society. 



9. The companion-cells of the phloem are completely filled with finely- 

 granular and easily staining protoplasm. Their nuclei are comparatively large. 

 Their appearance is that of secreting cells. Hence we may provisionally assume 

 that to them is assigned the function of secreting substances (probably enzymes) 

 to prepare the organic materials and render them suitable for introduction into 

 the tracheae and for transmission in these tubes. 



10. These secretions may be stored in the sieve-tubes, whose sieve-plates 

 prevent their passage along the bundle. The sieve-plates may be regarded as 

 partitions which allow the protoplasm to be withdrawn through their pores, but 

 at the same time have been rendered practically impei-meable by the remnant of 

 protoplasm and the callus left blocking the pores. 



References. 



1. Beccarini, p. — Intorno ad una p art i col a r it a clei vasi cribrosi nelie 



Papilionacee. Malpighia, vol. vi, 1892, p. 53. 



2. Dixon, Henry H. — On the Vegetative Organs of Yimda teres. Proe. Roy. 



Irish Acad., Ser. 3, vol. iii, No. 3, 1894. 



3. Dixon, Henry H. — The Transport of Organic Substances in Plants. Pre- 



sidential Address, Section K, British Association, 1922. 



4. Dixon, Henry H., and Ball, Nigel G. — Transport of Oi-ganic Substances in 



Plants. Nature, Feb. 23, 1922. 



5. Farmer, J. B.— Quoted by Sir W. T. Thiselton-Dyer (14). 



6. Hooker, Sir William H.— Quoted by Sir W. T. Thiselton-Dyer (14). 



7. CtARdiner, W. — On the Continuity of Protoplasm through the Walls of 



Vegetable Cells. Phil. Trans. R.S., vol. 174, 1893. 



8. Lloyd, Fras. E. — Development and Nutrition of the Embrj'o, Seed, and 



Carpel in the Date, Phoenix dactylifera L. Missouri Botanic Garden, 21st 

 Annual Report, 1910, p. 103. 



9. Pond, R. H. — Incapacity of the Date Endosperm for Self-digestion. Ann. 



of Bot., XX, 1906, p. 61. 



10. Reed, H. S. — A Study of the Enzyme Secreting Cells in the Seedlings of 



Zea Mays and Phoenix dactylifera. Ann. of Bot., xviii, 1904, p. 267. 



11. Sachs, J. — Zur Keimungsgeschiehte der Dattel. Bot. Ztg., No. 31, p. 241. 



12. Sargant, Miss E. — A Theory of the Origin of Monocotyledons founded on 



the Structure of their Seedlings. Ann. of Bot., xvii, 1903, p. 1. 



13. Strasburger, E. — Histologische Beitrage, Hft. III. Ueber den Leitungs- 



bahnen in den Pflanzen, i5. 193. 



14. Thiselton-Dyer, Sir W. T. — Germination of Double Cocoa-Nut. Ann. of 



Bot., xxiv, 1910, p. 223. 



