370 R- T. BAKER AND HENRY G. SMITH. 



Leaf Histology —Amongst Melaleucas there are several 

 differences which characterise the structure of the leaf 

 texture of this species. The palisade parenchyma is not a 

 distinct feature in a cross section, although it is more in 

 evidence on the underside of the leaf than towards the top 

 surface. The cells of the spongy parenchyma have circular 

 walls in a transverse section, as against the angular shape 

 of those of M. leucadendron, and this particular leaf sub- 

 stance is in greater proportion towards the petiole, although 

 in other parts of the leaf it is in equal proportion to the 

 palisade parenchyma. Near or close to the petiole, the 

 palisade parenchyma gives place entirely to spongy paren- 

 chyma. Stomata occur mostly in the lower portion of the 

 leaf and more especially on the inner or upper surface at 

 that portion of the blade. Another distinguishing feature 

 in this part is the strong development of papillose projec- 

 tions on the cuticle of the epidermal cells of that surface. 

 The vascular bundles are normally orientated, the phloem 

 facing the outer or under surface of the leaves, and are 

 entirely surrounded by a compact or coalesced body of 

 sclerenchymatous tissue exceeding in area that of the 

 bundle. These were doubtfully regarded as transfusion 

 tissue under M. uncinata, Part I of this series. The median 

 bundle is finally bounded towards the cuticle by spongy 

 mesophyll which thus makes a complete break in the con- 

 tinuity of the palisade parenchyma. 



Essential Oil.— The oil of this species consists largely of 

 dextro-rotatory pinene, cineol, a small quantity of ester, 

 and a sesquiterpene. It belongs to the pinene-cineol group 

 of Melaleuca oils, and resembles somewhat in general 

 characters the oil of M. nodosa, although it is richer in 

 cineol than the oil of that species. The yield of oil is some- 

 what small, so that M. gibbosa cannot be considered of 

 value as an oil producing tree. 



