134 Bulletin JARD. Bot. Buitenzorg, Série 111, Vol. V. Livr. 2. 



and the parenchyma surrounding the previously scattered bast is gradually 

 being occupied by bast cells. The parenchyma cells arranged in radiating 

 groups are not modified but are subjected to a centrifugal force which 

 results in séparation of groups of cells giving rise to cavities running up 

 and down the length of the root which in cross section are seen in the 

 form of radiating lacunae (Figure 53 Plate Vil and Figures 113 — 115 

 Plate XIV). The cavities in the early stages of formation appear in cross 

 sections as isolated splits or slits. Figure 113 Plate XIV shows a sector of 

 such a cross section with the fissures more or less arbitrarily disposed. 

 Radii projected from the center of the section would pass through one or 

 more such fissures. Where there is more than one fissure through which 

 the radius passes, thèse will ultimately coalesce to form a single air chamber. 

 The partitions or septa separating the chambers vary in thickness. They 

 may be one, two, three, four or more cells thick. .'Figures 114, 115 

 Plate XlVj. As a rule the cross-sectional length of the chamber is deter- 

 mined by the zone of bast just inside of the hypodermis on the one end 

 and by the zone of parenchyma cells whose long axes run parallel with 

 the circumference — a zone to which we hâve already referred. Occasionally 

 the lacunae are seen in cross section apparently as cavities that hâve not 

 separated entirely along the line of cleavage. While that may be true it 

 must be remembered also that the course of the lacunae up and down 

 does not run in a true straight vertical plane — that they do not necessarily 

 run the full length of the root but they may begin and end at any level, 

 so that in a cross section one may eut through the tapering ends of such 

 lacunae, (Figure 114 Plate XIV). The air spaces ramify throughout the root 

 affording a most efficient aerating System. 



With the release of mutual pressure from the polygonal thin walled 

 parenchymous cells resulting from the séparation along the lines already 

 indicated, the cells of the septa loose their polygonal form and become 

 rounded as is shown in Figures 114 and 115; also inter-cellular spaces 

 appear between adjacent cells. The inter cellular spaces afford easy com- 

 munication between air chambers. 



Freidenfelt to whose original work 1 unfortunately had no access 

 during this study is quoted by BiiSGEN (3-') as stating that the formation of 

 lacunae between layers of tissue is a characteristic of hydrophyllous roots 

 — also that the development of a strong hypodermis is found in such roots. 

 The root of Elaeis answers both conditions and its natural habitat, the 

 tropical forest of Africa and South America, places it in the category of 

 plants with hydrophyllous roots. 



The évidence taken from the free hand sections of living material and 

 from prepared and stained slides tends to support the schizogamous origin 

 of the air chambers in Elaeis. The présence of torn and shrunken cells 

 bounding the cavities is strong évidence for such an interprétation (Figure 1 14). 

 Such cells hâve been observed in the very early stages of lacunae formation 



