Callitriche. | HALORAGES. 159 
There seem to be two forms of this—one with a broad wing occupying a 
third of the whole width of the fruit, the other with a much narrower wing. 
The last-mentioned form was referred by Mr. Kirk to C. obtwsangula, Hegelm, 
Monog. Callit. 54, t. 3, £. 3, but this determination is clearly erroneous, the true 
obtusangula having rounded angles to the fruit, which is not at all winged. 
Orper XXVIIL MYRTACEA. 
Trees or shrubs, sometimes climbing. Leaves opposite, more 
rarely alternate or whorled, simple and entire, usually dotted with 
pellucid oil-glands and with a vein running parallel to the margin. 
Stipules generally absent. Flowers regular, usually hermaphrodite, 
solitary and axillary, or in axillary or terminal cymes panicles or 
racemes. Calyx-tube adnate to the ovary up to the insertion 
of the stamens, limb 4-5 or many-cleft or -partite, persistent or 
deciduous, imbricate or valvate, sometimes entire or closed in bua. 
Petals as many as the calyx-lobes, rarely wanting, inserted 
on a disc lining the calyx-tube. Stamens usually numerous, 
inserted on the disc with the petals; filaments free or connate at 
the base or united into separate bundles; anthers small, roundish. 
Ovary inferior or semi-inferior, crowned by a fleshy disc, some- 
times 1-celled with 1 or few ovules, more often 2- to many-celled 
with numerous ovules ; style simple; stigma capitate. Fruit either 
crowned by the persistent calyx-limb or marked by its scar when 
deciduous, usually a capsule loculicidally dehiscing into as many 
valves as cells, or a l- to many-seeded berry, more rarely dry and 
indehiscent. Seeds angular or compressed or cylindrical ; albumen 
usually wanting. 
A very large and distinct order, readily recognised by the opposite exstipulate 
entire leaves, furnished with a marginal vein, and filled with transparent oil- 
glands. Thespecies are mainly tropical or subtropical ; most abundant in South 
America and Australia, much less common in Asia and Africa ; more frequent 
in the south temperate zone than in the north, where they are decidedly rare. 
Genera about 80; species probably not exceeding 1800. The order includes 
many plants of economic importance. Some produce valuable spices, as cloves, 
allspice; or edible fruits, as the guava, the rose-apple, brazil-nuts, &c.; others 
yield aromatic essential oils, as eucalyptus, cajeput, &c. The bark of most of 
the species is more or less astringent. Some of the species of Hucalyptus attain 
a height of over 400ft., being probably the tallest trees in the world. Of the four 
New Zealand genera, Leptospermuwm extends through Australia as far as the 
Malay Archipelago; Metrosideros occurs in the Pacific and Malayan Islands, 
Australia, and South Africa; Hugenia is mainly tropical; and Myrtus mostly 
American. 
* Fruit capsular. 
Leaves small, alternate. Flowers solitary or fascicled .. 1. LeprospERMUM. 
Leaves larger, opposite. Flowers usually handsome, 
cymose 2. METROSIDEROS. 
** Fruit a berry. 
Flowers usually solitary. Embryo curved, with a long 
radicle .. * St He ete .. 3. Myrrus. 
Flowers cymose. Embryo thick and fleshy, radicle short 4. HuGEnta. 
