YampolskY: Stiidy of OU palm. 133 



Air chambers-origin. 



The root of tlie oil palm in gênerai conforins te the description of 

 monocotyledenoiis roots and no attempt wiil be made hcre to enter into 

 any great détail about the tamiliar parts of this organ. There are however 

 conspicuous features which merit close examination. The présence of 

 lacunae or air chambers, structures which we hâve noted for several forms, 

 are found in ail roots of Elaeis as a normal condition directly correlated 

 with definite physiological functions. Thèse lacunae (Figure 53, Plate VII, 

 Figures 119 and 120 Plate XV and Figures 113 to 115 Plate XIV) are 

 présent in the very youngest and oldest of plants irrespective of locality. 



The origin of thèse lacunae is not difficult to trace. By making cross 

 sections at varions levels from the tip upwards complète stages can be 

 secured. A section through the embryonic régions of the plerome and 

 the periblem shows that the cells are irregularly disposed and in an active 

 state of division. A section a little above the embryonic régions shows 

 the cells in a definite arrangement. Figure 54, Plate VII is a cross section 

 of such a région. The large epidermal cells are conspicuous in contrast 

 to the other cells. Contrary to the statement made by BùCHER and 

 FlCKENDEY (^), 1 was uiiable to find any root hairs in Elaeis developed 

 from the epidermis. In Figures 116 and 117 Plate XV two views of the 

 epidermal layer are seen in cross and longitudinal sections respectively. 

 The cells directly inward from the epidermis with strongly thickened walls 

 and which are suberized mark the outer boundary of the hypodermis that 

 is being developed. The layer of cells following those hâve not yet been 

 suberized. Then follow polygonal parenchyma cells and scattered among 

 the parenchyma cells are still larger polygonal cells which contain bundles 

 of raphides, presumably calcium oxalate. Bast cells (Figure 118 Plate XV) 

 hâve already begun to appear forming a somewhat irregular zone in this 

 stage. The conspicuous rows of radiating cells (Figure 54 Plate Vil) be- 

 ginning a little distance from the endodermis will ultimately be the seat of 

 origin of the lacunae or air chambers. The mutual pressure exerted by 

 the thin walled cells results in polygonal outlines. The inner boundaries 

 of thèse radiating groups of cells are marked by a zone of cells, seven or 

 more layers in thickness, whose long axes run at right angles to the 

 radius of the section. This zone of parenchyma extends to the endoder- 

 mis (Figures 53 and 54 Plate VII and Figures 114, 115 Plate XIV). Within 

 the endodermis are the xylem, phloem, parenchyma and pith cells. 



The gross détails of the root of f/«t'5/so-////;(^^/z5/s indicating the lacunae 

 hâve been published by DE WiLDEMAN (■*') taken from the notes of DE Briey. 



As one proceeds further upward from the growing point differentation 

 within the root goes on vcry rapidly. That part of the root becomes more 

 rigid as resuit of changes in tissue and cell structure. More layers of suber- 

 ized cells are added to the hypodermis, the bast cells increase in number 



