1915-16.] BOTANICAL SOCIETY OF EDINBURGH 77 



ing well with water was taken through the graded 

 alcohols to 90 per cent, alcohol. Sectioning was done by- 

 hand, and before proceeding to stain the sections were 

 placed in iodine for a few minutes in order to get rid of 

 any mercuric chloride. The stains used were iodine green 

 and picric fuchsine, or Bismarck brown and Ehrlich's 

 acid hfematoxylin. 



The points which were studied in connection with this 

 piece of research were the absorptive areas and the mechani- 

 cal and fundamental tissues ; the material did not permit of 

 a comparison of the vascular systems. 



Structure of the Adult Aerial Root of Monstera deliciosa. 



The central conducting portion of the aerial root consists 

 of alternating strands of xylem and phloem, with the 

 vessels increasing in size towards the centre. These 

 vascular strands are divided into groups of one or more 

 large vessels surrounded by smaller ones. The elements of 

 the protoxylem are spiral, and of the metaxylem the vessels 

 are scalariform, while the contiguous vessels are provided 

 with transverse pitted plates. 



The ground tissue of this root is completely sclerosed, 

 the cell walls being very thick and the markings well 

 defined. An irregular row of from one to three cells deep 

 of thick-walled pitted cells divides the outer cortex from 

 the inner cortex. On the outside border of this layer there 

 are cells rich in rhombohedral crystals of calcium oxalate. 



The cortex is composed of large polyhehric cells ; stellate 

 crystals of calcium oxalate are scattered throughout, but 

 they are more numerous towards the periphery. The 

 fibrous hairs so common in the Aroideae are found in 

 quantity in the intercellular spaces. Surrounding the 

 cortex is the thin-walled cambial tissue from which the 

 suberised layers are developed, and lastly there is the 

 piliferous layer which persists in the adult roots (cf. Van 

 Tieghem's description of the root of Monstera repens in his 

 paper on " Structure des Aro'idees," Annales des Sciences 

 Naturelles, sdr. 5, tome vi, p. 147). 



The adult roots of Monstera deliciosa grown in the other 

 four media, soil, water, gravel, and damp soil, show the same 

 general structure as the aerial root, but they differ in the 



