Palmae


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Related to Palmae: Labiatae, Umbelliferae, Arecales, Palmtree

Palmae

 

(also Arecaceae), a family of arboreal monocotyledonous plants. The trunk is usually unbranched and columnar and has a crown of leaves at the top. Palms reach a height of 60 m (for example, the wax palm is 50–60 m tall) and a diameter of 1 m (for example, the coquito). Some species of doom palm have branched trunks; other palms, such as the Colpothrinax, have urceolate trunks. Many palms are shrubs, since they develop numerous stems from axillary buds at the base of the trunk or along an underground rhizome. Certain palms do not have any surface stems or trunks, and only their leaves appear above the ground. Some palms are climbing lianas with long, slender stems. For example, lianas of the genus Calamus reach a length of 300 m and a diameter of 2–3 cm. Most palms have smooth trunks; however, some, including the hemp palm, are covered with the remains of petioles and ocreae, which have been shredded into fibers. The trunks of some species are thorny.

Palm leaves are alternate and either pinnate (fishtail palms have bipinnate leaves) or fan-shaped (if the axis of the leaf is extremely shortened). The petiole contains the ocrea. Pinnate leaves may exceed 15 m in length (for example, in the raffia palm). The talipot has the largest fan-shaped leaves, with a diameter of more than 5 m. All parts of the leaf may have thorns, and the lower segments of pinnate leaves sometimes are represented by spines. The leaf axis of most climbing palms continues into a tendril equipped with clawlike formations or reversely oriented spines.

Palms usually flower between the ages of five and 12 years. Some species, for example, the talipot, begin to flower only in their 30th to 50th year. The inflorescences generally are spadices or spikes; some species, however, have racemose or panicled flower clusters. The young inflorescences are enclosed by a large spathe and usually bear several additional small spathes. As a rule, the inflorescences develop in axils of leaves; a few palms develop very large apical flower clusters (in the talipot, the clusters reach lengths exceeding 6 m). The trunks of palms with apical inflorescences die after fruiting, sometimes leaving numerous offshoots at the base. (Such plants are said to be monocarpic.)

Palms are most commonly monoecious plants with small, tripartite, unisexual flowers. Occasionally the flowers are bisexual. The succulent or leathery lobes of the perianth, which are separate or, at times, partially fused, are green, white, or yellow. They are distributed in two circles or, less commonly, spirally. There are usually six stamens, arranged in two rings, and three carpels, usually fused into a three-celled ovary. As a rule, there are three ovules, of which only one develops and forms a single-seeded fruit. The fruits do not open and are either juicy or dry; the most common forms are drupes and berries. The seeds, which are large and have a hard endosperm, germinate without a dormant period. Upon germination, the cotyledon remains inside the seed and extracts nutritive substances from the endosperm.

There are as many as 240 genera of palms, embracing approximately 3,400 species. Most species grow in the tropics; only a few thrive in other climates. Only the hemp palm (Chamaerops humi-lis) is encountered in Europe—in Spain and Southern France. Paleobotanical evidence indicates that the range of Palmae formerly was much more extensive. Palms are found in the most diverse ecological conditions, including rain forests, seashores, savannas, and desert oases. Some species grow in the mountains at elevations to 3,000 m. (The wax palm is found in the Andes at elevations to 4,000 m.)

The economic value of palms is enormous. Many species are widely cultivated in tropical regions, providing, in a number of countries, the basic products needed by the population. The pith of the sago and miriti palms yields the starch sago. The fruits of the oil and coconut palms provide oils used in food and for industrial purposes. Date palms and various other palms yield edible fruits. Many palms are sources of sugar, wine, alcohol (from juices gathered by tapping the inflorescences), organic waxes, and vegetable ivory (from hardened nuts of the Phytele-phas and other species). The trunks provide valuable building and handicrafts materials. The leaves are used in the production of paper, roofing material, and such woven articles as baskets, pads, and mats. The leaves also yield fibers. Since ancient times, palms have been cultivated as ornamental landscape plantings or houseplants.

More than 20 species of palm have been introduced to the USSR, on the southern shore of the Crimea and on the Black Sea coast of the Caucasus. The species most resistant to cold temperatures are the Trachicarpus and Chamaerops. Cultivated palms are propagated from seeds or, for certain species, cuttings.

REFERENCES

Ginkul, S. G. “Pal’my Chernomorskogo poberezh’ia Kavkaza.” In Trudy po prikladnoi botanike, genelike i selektsii, vol. 24, fasc. 4, 1930.
Derev’ia i kustamiki SSSR, vol. 2. Moscow-Leningrad, 1951.
Saakov, S. G. Pal’my i ikh kul’tura v SSSR. Moscow-Leningrad, 1954.
Siniagin, I. I. Tropicheskoe zemledelie. Moscow, 1968.
McCurrach, J. C. Palms of the World. New York, 1960.
Corner, E. J. H. The Natural History of Palms. London, 1966

S. S. MORSHCHIKHINA

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