Palms are perhaps the most
striking plants in tropical floras. Their often tall, usually straight,
unbranched, woody stems topped by a spreading crown of long-stalked, sometimes
huge, featherlike or fanlike, pleated leaves distinguish them from nearly
all other forms of vegetation. The palm family is the only family in the
order Arecales and is one of the oldest of
flowering plants. The palms' fossil record
traces back to the Triassic Period, about 220 million years ago. Strict
application of the International Code of Botanical Nomenclature would make
Arecaceae the valid name for the palm family, but the name Palmae has been
accepted as a legitimate alternative. The palm family comprises nearly
2,500 species in 200 or more genera. They are widely distributed
in the tropics and subtropics; very few species occur in warmer temperate
regions. Most palm species occur in Asia (about 1,385 species), particularly
in the Indo-Malayan region, and in tropical America (about 1,147 species),
especially in northeastern South America. Only about 117 species are native
to Africa.
One of the hardiest of the tree palms is the windmill palm, Trachycarpus
fortunei, of eastern Asia, which is cultivated outdoors in milder maritime
climates as far north as Vancouver, Canada. The most cold-tolerant palm
is the needle palm, Rhapidophyllum hystrix, of the southeastern United
States: it has been known to survive temperatures of -21 degrees C (-6
degrees F).
In addition to the commonly recognized treelike forms, which may
reach 30 m (100 ft) high, there are those with prostrate or creeping stems
(Rhapidophyllum), those with stems completely underground (Nypa), and those
with vinelike stems (Desmoncus). The long, thin, ropelike stems of the
rattan palms, Calamus and Daemonorops, which may climb 60 m (200 ft) into
the treetops, are the rattan cane used commercially. The leaves of the
raffia palms, Raphia, are the largest in the plant kingdom, exceeding 20
m (65 ft) in length, and are the source of raffia fiber.
Palm flowers are typically small and may be borne singly, in pairs,
in threes (triads), in small clusters (cincinni), in small lines (acervuli),
or in large clusters (panicles). The flower cluster, or inflorescence,
is enclosed by a bract that ranges from thick and woody to paper thin.
This serves to protect the inflorescence and allow it to develop to maturity
with little outside interference, such as animal or insect predation. Palm
flowers may be bisexual but are usually unisexual. Palm trees are usually
monoecious, bearing both male and female unisexual flowers on the same
tree, but some species are dioecious, with separate male and female trees,
or polygamous, with both unisexual and bisexual flowers on the same tree.
Palm fruit is botanically a berry, nut, or drupe, depending in part upon
the structure of the flower ovary. The coconut (with husk) is a drupe,
a fruit technically like that of the peach but dry and fibrous instead
of fleshy.
Since prehistory, palms have
provided thatch for shelter; fibers for weaving, plaiting, and basketry;
timber for constructing buildings, tools, and utensils; leaves for clothing
and food; and sap for beverage. The sap drawn from tapping the unopened
flower bracts of several kinds of palm produces palm wine, or toddy, as
from Caryota urens; an alcoholic beverage called arrack, from Cocos nucifera;
or sugar, from Borassus flabellifer and Arenga pinnata. Foremost among
African palms is the date palm, Phoenix dactylifera, cultivated since ancient
times throughout the Middle East. Many countries use palm oil--as a vegetable
oil, in margarines and sweets, in pharmaceuticals, and in the manufacture
of soaps, candles, and lubricating greases. The oil palm tree, Elaeis guineensis,
native to Africa but now widely cultivated in other areas, is the most
important source of palm oil.
Reviewed by Michael J. Balick
Bibliography: Balick, M. J., ed., The Palm--Tree of Life (1988);
Balick, M. J., and Beck, H. T., eds., Useful Palms of the World (1990);
Fox, James J., Harvest of the Palm: Ecological Change in Eastern Indonesia
(1977); Jones
, The
palms are highly speciose, with an estimated 2500-3500 species in 210-236
genera (see Chapter 4). Variation in species
numbers
arises from disagreement between botanists as to the delineation of species
and genus boundaries. Regardless of the
exact
number of species, palms comprise a significant and diverse group that
ranks fourth or fifth in size (depending on which
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How
to Germinate Palm Seeds
