The Tree (16 page)

T
HE
M
IXED
B
AG OF
P
RIMITIVE
D
ICOTS

As you can see from the chart, the primitive dicots include seven orders. The three extreme outliers need not delay us too long. At least, the Amborellales does include one tree—which, like so much of botanic interest, lives in New Caledonia. It is aromatic, but it is only small. The Nymphaeales is the order of the waterlilies: of huge interest botanically and ecologically, but emphatically non-tree-like. The Australobaileyales are interesting as the possible sister group of all the other flowering plants—and because the order contains the family Illiciaceae, which includes the genus
Illicium.
From the bark of various species of
Illicium
comes the spice star anise.

The remaining four orders collectively form a group that botanists refer to as the magnoliid clade. All of them contain trees, and three of them contain some very significant trees indeed.

M
AGNOLIAS
, C
USTARD
A
PPLES
,
AND
N
UTMEG
: O
RDER
M
AGNOLIALES

The Magnoliales order contains around 2,840 species in six families, of which the three outlined here—Magnoliaceae, Annonaceae, and Myristicaceae—include highly significant trees.

Some traditional classifications list up to twelve genera in the Magnoliaceae.
¹
But Judd combines eleven of the traditional types into
Magnolia;
the other genus is
Liriodendron.
Between them they include 218 species, and they have the kind of distribution that we have already seen among the conifers: many in Southeast Asia, from the Himalayas out to Japan, and many more in the southeastern United States and Central America, with some in South America. Why are they spread out this way? Did they at some point leap the Pacific? Perhaps. But there are fossil Magnoliaceae in Europe and even in Greenland—which suggests that the family may once have spread more or less continuously from Southeast Asia to the Americas before the two continents drifted apart, and that they have simply died out in the middle of their range.

Magnolia
is, of course, magnificent, with some of the most stunning flowers of any tree—sometimes star-like, sometimes huge like waterlilies. Their greatest value for humanity is in horticulture; and I commend to you the magnificent botanic gardens in Yunnan, in southwest China, which has a hundred or so species. Some magnolias give serviceable timber. The bark and flower buds of
M. officinalis
of China are used medicinally and are a valuable export. (China is also one of the world’s greatest centers of biodiversity, and its potential for ecotourism is unsurpassable. It is up there with Africa, Madagascar, and Amazonia.)

Liriodendron
includes the two species of tulip trees—one Chinese
(L. chinense)
and one North American
(L. tulipifera).
Their leaves are strange and absolutely characteristic—like glossy, dark green versions of maple leaves, but with the pointed tip cut out. Their flowers are tulip-like, although difficult to appreciate since tulip trees can be big (the tallest in England is 36 meters) and the flowers are borne aloft. The American tulip tree yields a creamy timber, with streaks of olive green, black, pinkish brown, or even steely blue, from growing in mineral soils; it is much valued for carving, as well as for doors and suchlike. As a timber tree,
Liriodendron
is sometimes known as “yellow poplar” and is sold as “American whitewood.” Such names do it scant justice.

You can’t mistake the leaves of the tulip tree,
Liriodendron.

The 2,300 species of Annonaceae, arranged in 128 genera, form a glorious family widely spread through lowland tropical and subtropical forest. In many ways they seem wonderfully primitive. Their flowers are pollinated by beetles—which they have evolved to encourage: they have a fruity odor, and they reward their visitors with thick, fleshy petals for feeding on, and extra fleshy tissue that serves no purpose except to provide beetle food. Some flowers of the genus
Annona
are able to heat up—a fairly common trick among several plant families. This encourages the beetles to stay inside the flowers overnight and mate, so becoming covered in pollen. Various genera, notably
Annona
and
Rollinia,
provide marvelous fruits of the kind that seem primitive and in Cretaceous times doubtless were food for dinosaurs: big and pulpy, with many big seeds. Custard apple
(Annona cherimola),
with its gray, tessellated skin, is the best known of these fruits in the West. Others include the soursop and sweetsop. The fruits of
Monodora myristica
are sometimes used in place of nutmeg, and some Annonaceae with thick, fibrous bark are grown as ornamentals, at least in warm countries.

The third important family of the Magnoliales order is the Myristicaceae. It includes 370 known species in seventeen genera, which occur across the tropics: in South and Central America, across equatorial Africa, through south India and Southeast Asia, and into Queensland, Australia. The trees are usually dioecious (only one sex per tree) and although their flowers are small and inconspicuous they are pollinated by insects—beetles and thrips. Clearly they are very different from those of the Annonaceae or Magnoliaceae—illustrating that although flowers are one of the main guides to classification, they may nonetheless differ enormously even between closely related families.

The biggest genus is
Myristica,
with 125 species, centered on New Guinea.
Myristica fragrans
from the Molucca Islands of Indonesia is the most economically important of all the family. Its big seeds are nutmeg; the fleshy coating of the seed (the “aril”) is scarlet while it remains on the tree (although concealed inside a thick fruit with a pale green skin) but is a pale buff pink after drying and is the stuff of mace. The seeds of the Brazilian genus
Virola
are ground to make snuff that is hallucinogenic. (Perhaps the world needs more hallucinogens rather than less. The puritanical attitude of the West might more properly be seen as an offense against nature.)
V. surinamensis,
whose seeds are waxy, are used to make a type of butter for eating and for candles. So too are those of
Gymnacranthera farquhariana,
from India.

G
REENHEART
, S
TINKWOOD
,
AND THE
S
WEET
B
AY
T
REE
: O
RDER
L
AURALES

The Laurales order includes around 3,400 species in seven families, of which the most significant is the Lauraceae (named, incidentally, by Antoine-Laurent de Jussieu, who first made clear the monocot-dicot distinction).

The members of the Lauraceae family are mostly trees or shrubs. In all, there are around 2,500 species in 50 genera, a huge presence in tropical wet forests worldwide, and in the subtropics. They serve humanity in many ways: with extraordinarily nutritious fruits, many fine timbers, and a host of medicines and other drugs. The Lauraceae illustrate beautifully how biochemistry runs in botanical families.

Best known of all Lauraceae fruits is the avocado,
Persea americana,
native to Central America, and
P. drymifolia
from Mexico. It has more protein than any other fruit and is 25 percent fat. It also has a wonderful strategy to prevent inbreeding. As with other Lauraceae, it is pollinated by insects. It has two kinds of flowers, inventively dubbed A and B; some individuals have A flowers and some have B flowers. The stigmas of A flowers are receptive to pollen only on one particular morning, while the anthers of A flowers do not release their pollen until the afternoon of the same day. In B flowers, the stigmas are receptive on one afternoon, while pollen is not released until the following morning. So A flowers can be pollinated only by B flowers, and B flowers can be pollinated only by A flowers.

Many Lauraceae have oil cavities in their leaves and elsewhere, and many are aromatic. Thus the family includes the bay trees
(Laurus nobilis),
sassafras
(Sassafras albidum),
cinnamon
(Cinnamomum verum),
and camphor
(C. camphora),
once much used in mothballs (though modern mothballs are made of naphthalene)—one of many examples of a tree’s own insect repellent turned to human use.

Among the many valuable timber trees in the Lauraceae family is the Queensland “walnut,”
Endiandra palmerstonii,
which grows to a magnificent 40 meters or more and whose timber resembles that of the European walnut (which comes from the quite different Juglandaceae family). It has pinkish sapwood and pale to dark brown heartwood, streaked with pink or purple-black—much prized for furniture of the boardroom kind. The mangeao of New Zealand’s North Island
(Litsea calicaris)
is another giant (40 meters or more), giving cream to pale brown timber that is favored for everything from turnery to dance-hall floors to pit props in mines—and also for excellent veneers for export. Imbuia
(Phoebe porosa)
from Brazil is yet another forest giant (up to 40 meters) with a dark brown, fine-grained, lustrous timber that again is much coveted for high-class joinery.

The many fine trees of the genus
Ocotea
are prized both for their beautiful timber and for their broader biochemistry. South Africa’s stinkwood
(O. bullata)
is 18 to 24 meters tall in the forest, yielding a dark timber with a fine grain that is indeed malodorous when freshly worked but settles down when dried.
Ocotea usambarensis,
from Kenya, is camphorwood. It grows up to 45 meters tall, yields a greenish-brown timber that matures to deep brown, smells of camphor, and is much favored for making wardrobes, effectively with the mothballs built in. (I have found, in travels with tropical loggers, that many trees are surprisingly smelly when first cut, and not always pleasantly so.)

But the most famous of all the Lauraceae timbers comes from the greenheart
(O. rodiaei),
the pride of Guyana. It, too, reaches up to 40 meters, with a long cylindrical trunk that may be 25 meters tall and a meter in diameter. The sapwood is pale yellowy-green, the heartwood light olive to dark brown, often streaked with black. Greenheart is highly versatile: much favored in maritime circles for jetties and groins, and in ships for planking and stern posts, but also for turnery and the butts of billiard cues. It is used to make longbows, too, the technology of which has come on apace since the English first juxtaposed the heartwood and sapwood of yews. Modern longbows are laminated, and greenheart often forms the central layer.

In addition, the nut of the greenheart yields a material called “tipir,” which the native people of Guyana have long employed as a medicine. The Wapishana tribe grates the nuts and uses the extract to stop hemorrhages, prevent infections, and as a contraceptive. In the late 1990s, however, an American entrepreneur, after spending time with the Wapishana, tried to patent tipir as an antipyretic useful in preventing flare-ups of malaria, and perhaps for treating cancer and AIDS. The tribe accused him of theft: “biopiracy.” The dispute rumbles on. Meanwhile greenheart, precisely because it is wonderful in so many ways, is being seriously overlogged. But still it is outstanding even among the distinguished family of the Lauraceae, which are huge players in tropical forests and economies worldwide.

W
INTER’S
B
ARK AND
W
HITE
C
INNAMON
: O
RDER
C
ANELLALES

There are only two families in the Canellales order. The Winteraceae family includes up to 120 species (no one is quite sure) in seven or eight genera, largely from around the coasts of South and Central America, eastern Australia, and New Guinea, plus one in Madagascar. Several have peppery leaves and bark that are said to be medicinal; best known is Winter’s bark
(Drimys winteri),
which was once used to prevent scurvy. The wood of the Winteraceae is strange: the conducting tissue of the xylem contains only tracheids—rows of cells with perforated ends—as in a conifer. They do not lose the cell walls at the ends to form the continuous tube-like vessels that are more typical of broadleaves. But it is not clear whether this arrangement is primitive or secondary; the ancestors of the modern Winteraceae may have had vessels, which may subsequently have been lost. As we have seen, evolution often leads to simplification, and several other groups of flowering trees, unrelated to the Winteraceae, have wood with tracheids rather than vessels.