EOOTS OF CERTAIN PALMS. 285 



EXPLANATION OF THE PEATES. 



end., endodermis ; i.sp., intercellular space; i.sir., isolated strand; p., phloem ; l.r., lateral root ; 

 scl., sclerenchyma ; st., a complete stele ; v., vessel of the wood. 



Plate XIX. 



Figs. 1-6, Diagrams illustrating various types of transverse section of Areca roots ; tliese types are 

 distinguished merely for convenience, as there is perfect continuity of transition. The lines 

 end. represent the endodermis, and with the aid of figs. 7-9 give an indication of the general 

 disposition of the vascular system. X 1^ diam. 



Fig. 1. From a transverse section of a normal subterranean root of Areca, showing continuous endo- 

 dermis and concentrated vascular cylinder. 



Figs, 2-5. From sections of the same, somewhat tapering, aerial root of Areca. The arrows indicate 

 corresponding points. 



Fig. 2, From a section 15 millim. from the apex; the vascular cylinder is more bulky, and relatively 

 nearer the periphery than in fig. 1 ; the endodermis is almost circular in outline and is 

 continuous. 



Fig. 3. From a section 17 millim. from the apex; the outline of the endodermis is markedly not 

 circular and is discontinuous at several places ; it is, however, continuous at the point indi- 

 cated by the arrow ^ (see figs. 7 & 10). 



Fig, 4. From a section 115 millim. from the apex ; the endodermis is more markedly abnormal in out- 

 line and more discontinuous ; at the point indicated by the arrow, the endodermis is almost 

 discontinuous (see figs. 8 & 11). 



Fig. 5. From a section 150 millim. from the apex; the endodermis shows even more marked abnormality 

 in outline and greater discontinuity ; it is quite discontinuous at the point indicated by the 

 arrow (see figs. 9 & 12). 



Fig. 6, Diagram of a transverse section of a thicker aerial root of Areca, showing greater complexity of 

 structure; a small complete stele {st}j is indicated by the continuous eudodermal outline. 

 This stele is drawn in greater detail in fig. 13. 



Figs, 7-9. Diagrams to illustrate the disposition of tissues in the neighbourhood of the points indicated 

 by the arrows in diagrams 3-5 respectively ; xylem and sclerenchyma are shaded dark ; phloem 

 and parenchyma, light ; large vessels of the wood are shown unshaded and with double contour- 

 lines ; large intercellular spaces, unshaded and with broken contours ; endodermis is repre- 

 sented by dark lines ; i.st. is an isolated strand traversing the pith, x 25 diam. 



Figs. 10-12. Drawings illustrating in greater detail the tissues in the neighbourhood indicated by the 

 arrow in figs. 3 and 7, 4 and 8, 5 and 9 respectively ; dots in cells indicate that they belong 

 to endodermis. X 200 diam. 



Fig. 10 shows the endodermis continuous ; the cells are young, and their walls not much thickened. 

 Pig. 11 shows the endodermis merging into sclerenchyma and almost discontinuous. 

 Fig. 1 2 shows the endodermis quite discontinuous. 



