1996 - The Island of the Colorblind (32 page)

(In fact, coconut crabs do climb tall palm trees, and cut off the coconuts with their massive claws.)

89
It used to be held that cycads were wind-pollinated, like ferns and conifers, though early authors (including Chamberlain) had occasionally been struck by the presence of certain insects in or near the male cones at the time of pollination.

In 1980, Knut Norstog and Dennis Stevenson, working at the Fairchild Tropical Garden in Miami, were struck by the failure of many introduced cycads there to produce fertile seeds, even though healthy male and female plants had been planted just a yard or two apart, whereas the native
Zamia
was quite fertile. They found that snout weevils would feed as larvae on the male
Zamia
cones, emerging as adults by boring through the microsporophylls, covered with pollen. Could this be the way in which the female cones were pollinated?

Stevenson and Norstog, along with other researchers (Karl Niklas, Priscilla Fawcett, and Andrew Vovides), have confirmed this hypothesis in great detail. They have observed that weevils feed and mate on the outside of the male cone and then enter it, continuing to feed not on the pollen, but on the bases of the microsporophylls. Their eggs are laid, and larvae hatched, inside the microsporophylls, and the adult weevils finally chew their way out through the tips of the sporophylls. Some of these weevils go to the female cones, which exude a special warmth and aroma when they are ready for pollination, but the weevils cannot feed here, since the female cones are toxic to the insects. Crawling into the female cone through narrow cracks, the weevils are divested of their pollen and, finding no reason to stay longer, they return to the male cones.

The cycad thus depends on the weevil for pollination, and the weevil on the cycad cones for warmth and shelter – neither can survive without the other. This intimate relationship of insects and cycads, this coevolution, is the most primitive pollination system known and probably goes right back to the Paleozoic, long before the evolution of flowering plants, with their insect-attracting scents and colors.

(A variety of insects can pollinate cycads, mostly beetles and weevils, though one species of
Cycas
is pollinated by a bee – giving the possibility, one likes to think, of a delicious cycad honey.)

90
One cannot think of these beautiful adaptations without feeling how excellent cycads are, in their own way, and how meaningless it is to see them as ‘primitive’ or ‘lower’ plants, inferior in the scale of life to ‘higher’ flowering plants. We have this almost irresistible sense of a steady evolutionary advance or progress (culminating, of course, in nature’s ‘highest’ product – ourselves), but there is no evidence of any such tendency, any global progress or purpose, in nature itself. There is only, as Darwin himself insisted, adaptation to local conditions.

No one has written of our illusions about progress in nature with more wit and learning than Stephen Jay Gould, especially in his recent book,
Full House: The Spread of Excellence from Plato to Darwin
. They lead us, he writes, to a false iconography of the world, so that we see the Age of Ferns succeeded by the Age of Gymnosperms, succeeded by the present Age of Flowering Plants, as if the earlier forms of life had ceased to exist. But while many early species have been replaced, others continue to survive as highly successful, adaptable life forms, as with ferns and gymnosperms, which occupy every niche from rain forest to desert. If anything, we are really, Gould insists, in the Age of Bacteria – and have been for the last three billion years.

One cannot look at a single lineage, whether of horses or hominids, and come to any conclusions about evolution or progress, as Gould shows. We must look at the total picture of life on earth, of every species, and then we will see that it is not progress which characterizes nature but rather infinite novelty and diversity, an infinity of different adaptations and forms, none to be seen as ‘higher’ or ‘lower.’

91
Darwin was the first to argue that dispersal of seeds by sea water might be an important means of their distribution, and made experiments to explore their ability to float and survive salt water. Many seeds, he found, had first to dry but then might float for remarkably long periods: dried hazelnuts, for example, floated for ninety days and afterwards germinated when planted. Comparing these time periods with the rates of ocean currents, Darwin thought that thousand-mile ocean journeys might be common for many seeds, even if they had no special flotation layer (like cycad seeds). ‘Plants with large seeds or fruit,’ he concluded, ‘generally have restricted ranges, fand] could hardly be transported by any other means.’

Driftwood, he noted, might sometimes serve as a transport across the seas, and perhaps icebergs too. He speculated that the Azores had been ‘partly stocked by ice-borne seeds’ during the glacial epoch. But there is one form of oceanic transport, Lynn Raulerson suggests, which Darwin did not consider (though he would have been fascinated had it come to his attention), and this is transport by rafts of pumice, blown into the ocean by volcanic eruptions. These may float for years, providing transport not only for large seeds but for plants and animals as well. A vast pumice raft, stretching across the horizon, with coconut palms and other vegetation, was reportedly seen off Kosrae three years after Krakatau blew.

It is not enough, of course, for seeds to arrive; they must find conditions hospitable for colonization. ‘How small would be the chance of a seed falling on favourable soil and coming to maturity!’ Darwin exclaimed. The Northern Marianas – Pagan, Agrihan, Alamagan, Anata-han, Asuncion, Maug and Uracas – are doubtless visited by cycad seeds, but are too unstable, too actively volcanic, to allow them to survive and establish a viable colony.

92
The history and naming of the oceanic cycads is a story at once picturesque and confused. Surely Pigafetta, sailing with Magellan, must have observed the cycads of Guam and Rota, but if he did, his descriptions are too vague for us to be certain. It needed a botanical or taxonomic eye to demarcate cycads in the first place, from the circumambient palms around them. It was not until the next century that such botanical skills appeared, and then they appeared, with a sort of synchronicity, in two men, Rheede and Rumphius, whose lives and interests ran parallel in many ways. Both were officers of the Dutch East Indies Company. It was Rumphius who first described a cycad, on the Malabar coast in 1658. It was Rheede, his younger contemporary, who was to become governor of Malabar and publish a
Hortus Indicus Mal-abaricus
in the 1680
s
(after Rumphius’ own manuscript for a
Hortus Malabaricus
was destroyed in a fire). Rumphius’ and Rheede’s cycads were taken to be the same, and both were called
Cycas circinalis
by Linnaeus. When the French botanist Louis du Petit-Thouars identified a cycad on the east coast of Africa in 1804, it was natural that he should call this
C. circinalis
too, though it would be recognized as a distinct species and renamed
C. thouarsii
a quarter of a century later.

In the past few years there has been an effort to reexamine the taxonomy of the Pacific cycads, a task made peculiarly complicated, as Ken Hill notes, by ‘the successive recolonization of areas by genetically distinct forms…facilitated by aquatic dispersal of the buoyant seeds.’

Most botanists now are disposed to confine the name
C. circinalis
to the tall Indian cycad (that originally figured in Rheede’s
Hortus
), which grows inland and lacks buoyant seeds. This at least is Hill’s formulation; he sees the Western Pacific cycads as belonging to the
C. rumphii
complex, and the Marianas cycad, which he has named
C. micronesica
, as a unique species within this complex. David de Laubenfels, a cycad taxonomist at Syracuse, agrees that
C. circinalis
occurs only in India and Sri Lanka, but feels that Guam cycad belongs to an earlier-named species,
C. celebica
. Since, however, the Guam cycad has been called
C. circinalis
for two centuries, the likelihood is that it will continue to be called this, and that only botanists will insist on using its ‘correct’ name.

93
Aboriginal forests, cycad forests, seem to excite feelings of awe and reverence, religious or mystical feelings, in every culture. Bruce Chatwin writes of Cycad Valley, in Australia, as ‘a place of immense importance’ on some aboriginal songlines and a sacred place to which some aboriginals make their final pilgrimage before death. Such a scene, of final meetings and dyings beneath the cycads (‘like magnified treeferns’), forms the ending of
The Songlines
.

94
The term ‘deep time’ was originated by John McPhee, and in
Basin and Range
he writes of how those most constantly concerned with deep time – geologists – may assimilate a sense of this into their inmost intellectual and emotional being. He quotes one geologist as saying, ‘You begin tuning your mind to a time scale that is the planet’s time scale. For me, it is almost unconscious now and is a kind of companionship with the earth.’

But even for those of us who are not professional geologists or paleontologists, seeing ferns, ginkgos, cycads, forms of life whose basic patterns have been conserved for eons, must also alter one’s inmost feelings, one’s unconscious, and produce a transformed and transcendent perspective.

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