LI. MYRTACLrE. 
607 
b! ucalyptux.] 
passing through every gradation from that to numerous parallel diverging or 
transverse veins, always converging into an intramarginal vein, either close to or 
more or less distant from the edge, the intermediate reticulate veinlets rarely very 
prominent, and scarcely any when the primary veins are closely parallel. 
Flowers large or small, in umbels or heads, usually pedunculate, rarely reduced to 
a single sessile flower, the peduncles in most species solitary and axillary or 
lateral (hy the abortion of the floral leaves) either at the base of the year’s shoot 
below the leaves or at the end of the older shoot above them. Bracts and 
bracteoles when present so early deciduous as only to have been observed in a 
very few species. 
With the exception of two species extending to Timor, and two or three or perhaps one 
single somewhat doubtful species from the Indian Archipelago, the Eucalypti are all Austra- 
lian, and constitute a large portion of the forest vegetation. Their size and abundance, as 
well as the great value of their timber and other products, cause them to be well known to 
colonists under their local appellations of Gum, Mahogany , and Box-trees, Stringy -harks, Iron- 
barks, Ac. The extraordinary differences in the foliage of many species at different periods of 
their growth add much to the ordinary difficulties arising from the gradual transition of 
varieties, races, or species one into the other. The old division of the genus according to the 
opposite or alternate leaves is now found to be quite fallacious, so many species having them 
opposite at an early stage and alternate when full grown ; the second character generally made 
use of in books, the comparative length of the operculum and calyx-tube, is too indefinite for 
practical use. The groups have been established in the first place upon the form of the anthers 
and secondly upon that of the fruit, and in some cases on the inflorescence or the calyx. It 
must be admitted, indeed, that these groups, distinct as they may be in the typical species, pass 
very gradually into each other through intermediate forms, but I have endeavoured to supply 
cross-references to facilitate the determination of dried specimens in doubtful cases. 
I have thought it generally useless to describe the branchlets terete or angular, for in those 
species such as E. pruinosa, E. tetragon a, E. tetraptera, &c., where the angles are often so 
prominent as to be almost transformed into wings, there occur branches, often on the same 
specimen, quite terete. 
The form, size and venation of the leaves described has always been taken from those of the 
flowering branches of what have been supposed to be adult trees or shrubs ; when not stated to 
the contrary, they are always alternate and petiolate. A great majority of the species are now 
known to have on the young sapling, or even on adventitious barren branches of older trees, 
opposite sessile broad or cordate leaves passing gradually [into the ordinary alternate petiolate 
narrower ones. It appeared quite useless in any manner to describe these sapling leaves in the 
several species where they have been observed, for they present at once the greatest similarity in 
the corresponding leaves of different species and the greatest dissimilarity in the different leaves 
of the same species or specimen. Where in the following pages the leaves are described as 
opposite and sessile, it is meant that they retain that form on the flowering branches. So also 
in the venation, characteristic as it often is in the lanceolate leaves, the specific modifications 
disappear in a great measure as the leaf gets broader, and it is only very rarely that there are 
any appreciable specific differences in the venation of the sapling leaves. A very few at that age, 
especially in the Corymbose series, appear to be already alternate, but to have the lamina 
peltately inserted on the petiole above the base, but data on that point are but very scanty. 
Diagnostic characters are sometimes taken from the position of the leaves, horizontal or 
vertical, and the comparative colour of their surfaces, dark above and pale underneath or 
similar on both sides, but this can rarely be ascertained from dried specimens. In general it 
would appear that the horizontal leaves have the two surfaces different and the veins very 
divergent or transverse, and the vertical leaves have the surfaces similar and the veins oblique ; 
so that where the leaves of the adult tree are alternate lanceolate and foliate with oblique 
veins they are usually vertical, whilst the opposite ones of the sapling of the same species are 
horizontal. 
The inflorescence is often characteristic of species or even of groups, but cannot always be 
taken absolutely in single specimens. The umbels are as a rule universal, but are always in a 
very few large-flowered species, and occasionally in others, reduced to a single flower. The 
length of the peduncle supporting it, either absolute or compared to that of the petiole, to which 
importance is given in old diagnoses, appears to be rarely available as a specific character. 
Karely above lin., generally varying from \ to Jin. and sometimes entirely disappearing, it is 
only in the few cases where it is constantly long or short as compared to these dimensions that I 
have referred to it. These peduncles with their umbels are, however, in their general arrange- 
ment, of some importance, constituting three types: — 1, axillary or lateral, that is, solitary in 
the axils of the leaves, or along the branchlet above or below the leaves; 2, several together in 
short simple panicles at the end of the branchlet or in the axils of the leaves ; and 3, in a 
compound terminal corymbose panicle.. But these forms appear to pass into each other very 
much in imperfect specimens. In the first and simplest form, the floral leaves of the upper- 
