AUSTRALIAN MELALEUCAS AND THEIR ESSENTIAL OILS. 197 



(b) Histological. — The anatomical characters of the leaves 

 of this species present many interesting features that may 

 probably prove of value in the histology of this group of 

 Myrtacese, both for taxonomic as wellas phylogenic purposes. 

 Of those species of the genus so far examined, this one 

 possesses histological characteristics entirely its own, and 

 which apart from morphological and chemical characters, 

 are in our opinion almost sufficient even for specific dis- 

 tinction. The dozen or so figures submitted with this 

 paper are typical of a large number of sections made of 

 various magnifications. 



The leaves when examined macroscopically are found to 

 be irregularly and numerously marked with dark dots. 

 These are the oil glands. It is the configuration of the 

 leaves (terete) that gives the circular outline to the trans- 

 verse sections. One of the reasons for taking up the histo- 

 logical side of the subject was to ascertain the disposition 

 and other data concerning the oil glands, and also if possible 

 to trace the origin of the chemical constituents. 



The most important new features to be noted are 

 (1) the conical cells of the epidermis, (2) the transfusion 

 tissue of the stele, and (3) the endodermic cells in the leaf 

 substance. These are explained in detail under the descrip- 

 tion of each figure. 



Longitudinal Sections. — Fig. 1 is a longitudinal section 

 with a 25 magnification cut clear of the stele or mid-rib. 

 This illustration was selected for reproduction as it gives 

 a good idea of the numerous glands irregularly distributed 

 throughout the leaf tissue; whilst figure 2 shows the 

 appearance of a section magnified 80 times, cut through 

 the medullary bundle in the plane of the phloem. This 

 picture more particularly emphasises the irregularity of 

 distribution of the glands, for here, the three sectioned are 

 all on one side without any collateral ones. The conical 



