ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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thus in E. hsemostoma , E. goniocalyx , E. phlebophylla and E. Moorei the 
glands are flattened at right angles to the leaf-surface, and are confined 
to the palisade-parenchyma. In E. intermedia and E. corymbosa they 
are in the spongy mesophyll, and are narrowed towards the epidermis. 
In E. piperita , E. aggregata , E. hemiphlora and E. Smithii the glands 
extend right across the leaf. In E. robusta and E. resinifera they are 
large and directed towards the upper surface ; while in E. maculata , 
E. citriodora and E. siderophloia they are small and directed equally 
towards both surfaces. Deep-seated glands are characteristic of the 
petioles. The glands are round, ovate and elliptical in shape, the most 
Highly magnified median section of an oil-gland in an intermediate 
stage of development. The separation of the interior cell-mass 
(in section) from the wall of the cavity is quite pronounced. 
An extremely thin lid-cell is seen at the top of the gland. The 
groups of small cells on either side of the gland indicate vascular 
bundles. E. Smithii Baker, x 400. 
common form being ovate with the apex towards the upper or lower 
surface. The formation of oil is the result of alteration of the cell- 
contents by a schizolysigenous process. The “lid-cells” differ from 
those of the glands of the Rutaceae in their lack of definition ; it is 
often difficult to decide as to which are true epidermal cells and which 
are the “ lid-cells.” The oil is not always in the form of droplets, but 
may be more or less granular and lining the cavity or contracted to one 
side ; in the first place it is analogous to a chemical precipitate in the 
presence of a protein body which acts as a colloid and prevents the 
formation of drops ; finally, it forms an emulsion, which is diffused 
throughout the secretory cavity. S. G. 
