198 FAMILIES OF FLOWERING PLANTS 
the tropics, with a few forms extending into temperate lands. North 
America, for instance, has but 4 genera and about a dozen species, and 
these mostly confined to Florida. Australia possesses a number of pecu- 
liar and striking genera, among them Eucalyptus, a genus embracing 
about 160 species. They are usually tall trees, with narrow, leathery 
leaves. One species, the white peppermint-tree or giant gum-tree (Lf. 
amygdalina), is, according to the late Baron von Mueller, probably the 
loftiest tree on the globe, attaining a height of 475 feet and a diameter 
of 15 feet. This and many other species of Hucalyptus are of the greatest 
economic importance, furnishing timber for a wide variety of uses, as well 
as various oils, resins, acids, tannin, etc. Hucalyptus is thought to be 
of value in malarial regions in absorbing or warding off noxious emana- 
tions ; hence, several are known as fever trees. Some 70 or 80 species of 
Eucalyptus have been more or less extensively introduced on the Pacific 
Coast, but only a few, suchas E. polyanthema, E. globulus and E. robusta, 
are most abundant; all are of rapid growth. 
Among the many economic products of this family we may mention 
allspice or pimento, the product of Eugenia Pimenta or Pimenta 
officinalis, a tree of Mexico and the West Indies. Allspice consists of the 
fruits gathered before they are quite ripe and dried in the sun. The 
cloves of commerce are the dried flower buds of Eugenia caryophylla, a 
tree originally of the Moluccas, but now widely cultivated in the East and 
West Indies. The guava tree (Psidium Guajava) of tropical America 
produces the well-known guava fruits of tropical countries. The myrtle 
of the ancients is Myrtus communis, a tree of the Mediterranean region. 
Family Melastomaceae. Melastoma Family. This is also an 
Fig 174. The Yellow Deer-grass (Rhexia lutea.) 
immense family, which embraces about 150 genera and 2500 species. They 
are herbs, shrubs or trees, with mainly opposite 3-9-ribbed leaves with- 
