The flowers are numerous, small, symmetrical, uncoloured, or obscurely so, six-parted, and hermaphrodite or polygamous. They are produced in a spadix from the axils of the leaves, and are generally enclosed in a spathe or sheath. The ovary or seed-vessel is three-celled or three-lobed, but the fruit is generally one-seeded from abortion, and the seed is large and albuminous with a fibrous or fleshy covering.
Palms are almost exclusively tropical plants, very few species being found in the temperate zone, and those only in the warmer parts of it, while the nearer we approach the equator the more numerous they become both in species and individuals. Dr. Martius, a Prussian botanist and traveller in South America, has published a magnificent work in three folio volumes, entirely devoted to the Botanical history of this family of plants. He divides the portion of the earth which produces palms into five regions, namely,—
The North Palm Zone, extending from the northern limit of Palms to the tropic of Cancer.
The transition North Palm Zone, from the tropic of Cancer to 10° north latitude.
The Chief Palm Zone, from 10° north to 10° south latitude.
The transition South Palm Zone, from 10° south latitude to the tropic of Capricorn, and
The South Palm Zone, from the tropic of Capricorn to the southern limit of the family.
The Northern limit of Palms is, in Europe 43° of latitude, in Asia 34°, and in America 34°.
The Southern limit is 34° in Africa, 38° in New Zealand, and 36° in South America.
To the north of the tropic of Cancer there are 43 species of Palms known, and to the south of the tropic of Capricorn only 13, while as we advance from either side towards the equator the number increases, until in the Chief Zone, between 10° north and 10° south latitude, there are more than 300 species (see Frontispiece Map).