Dry Storeroom No. 1 (28 page)

Although the fungi collections moved to Kew Gardens, the lichens stayed behind in South Kensington, along with the other Crypts. They reside in their folders in the polished cabinets up in the “gods” of the Natural History Museum. Their systematic study goes back to Erik Acharius, a marvellous artist, who divided the original single lichen “genus” into forty, and thereby alerted the botanical world to their intriguing variety of form. For many years of my career the lichen man in the Natural History Museum was Peter James, diffident master in the art of their identification. With his trim beard, half-moon specs and amiable if distrait manner, he was almost exactly what a member of the public might imagine a museum academic to be like. There are more lichen species than you can shake a stick at, most of them passed by unnoticed in the field even by the most broad-minded naturalist. The British Checklist lists 2,272 species of lichens for these islands alone. Peter’s name is still spoken in hushed tones by the lichen community, since he has a preternatural ability to identify the most obscure species from memory. His successor, William Purvis, is as devoted to the cause of these under-studied organisms.

Lichens are particularly important as indicators of pollution because they readily absorb heavy metals into their tissues. They simply mop up elements like lead and cadmium. Lead was formerly present in appreciable quantities in petroleum spirit. In Britain it was practical to assay the damage done to the environment by mapping lichen species; most are unable to tolerate lead pollution for long, but those that can proliferate at the expense of others. The species plot out the state of the environment. It is extraordinary to see how precisely the lead pollution traced the course of trunk roads, forming a series of “corridors” with low lichen diversity criss-crossing the landscape. However, at least the lead content falls away laterally from the roads themselves. It is a wise precaution not to eat mushrooms picked by main roads, as high lead content has been associated with loss of brain function. The introduction of lead-free fuel received a boost from such findings. Far wider regional pollution across industrial areas is also faithfully recorded by these humble living patches. Inner cities can be very low in species as a result of the pollution from the “dark, satanic mills” of the last 150 years. As you move westwards across the British Isles, the number of lichens increases. The dominant weather systems move in from the clean Atlantic Ocean, flushing most pollutants eastwards, and the lichens revel in the moister atmosphere in the west. In the old oak forests in North Wales every boulder is dappled with lichens, while the twisted oak branches are heavily draped with leafy and feathery forms. Some of these lichens yield vegetable dyes with lovely natural colours, yellows especially, so in addition to dressing the trees, lichens might well help to dress us, too. Around the old mines on the hillsides nearby, other lichen species take up noxious elements or pollutants, for which they seem to have a particular affinity. These can now be accurately assessed using modern mass spectrometry (seepp. 236–37). They are use ful things, these unspectacular lichens, for diagnosing the health of the planet. As we have seen so often before, an apparently arcane expertise in an organism that would be passed by unnoticed by many relates to important contemporary issues.

Many lichens also grow very slowly, some just a few millimetres a year, and some even less than a millimetre. It is an interesting problem how to determine this rate of growth. One way to estimate the average growth rates is to use gravestones. These memento mori are a favourite habitat for lichens—indeed, there are some species that are now hardly found outside old churchyards. This is partly because many of these sacred acres have escaped chemical spraying or artificial fertilizer for decades or longer. As we have seen, lichens are unusually sensitive to all pollutants, even those of alleged benefit to farmers. Some churchyards are little patches of medieval habitat. Lie back beneath an old yew tree, and imagine priests and squires and villeins going about their Sunday business. A gravestone includes that very useful piece of information—a date. When erected they are pristine, but soon time and lichens make their mark. Lichens on flat gravestones tend to grow outwards in a regular circle, so the diameter of the circle is proportionate to its age. The largest circle found on a gravestone of a particular date will give an approximation to the maximum rate of growth. There will be a certain range of variation as a consequence of local conditions, and variation in the time of first colonization. Furthermore, as time passes, new species of lichen will join the gravestone habitat—and younger rings will “cut” through older ones as they grow, so revealing the order of succession of colonization. A good gravestone will accordingly yield a complex narrative, and many gravestones will provide usable statistics. Rates can then be applied to other sites. The use of lichens in dating is known as lichenometrics. Although not without its critics, lichenometrics has revealed some interesting figures. It seems that lichen growth rate has speeded up in high latitudes since the industrial revolution, and that this may be connected with global warming. Because they can be found nearly everywhere and grow so slowly, lichens are potentially a ubiquitous biological “diary” that records changes to the environment and atmosphere on the century scale. They are the Crypts’ answer to the tree rings on that ancient giant
Sequoia
trunk on display outside the Botany Department.

As with just about every other field of study mentioned in this book, the molecular revolution has forced us to rethink ideas about the relationships of lichens. Molecular evidence shows that fungi have become “lichenized” on many occasions: to put it another way, they have repeatedly made a contract with algae to enter into their special partnership. The great majority of such fungi are “waxy cup” ascomycetes (see Chapter 2); this is easy to see on those lichen species that bear little red or yellow cups on their surfaces, because they are not very different in appearance from the spore-bearing fruit bodies of their relatives, which can be found on forest paths or compost heaps. Next time you are in a country graveyard, peer closely at a headstone and you will be almost sure to see these little coloured cups or plates on an encrusting lichen. A few gilled, mushroom-like fungi have also taken this curious evolutionary path. On the other hand, the “algal” partners of the lichen symbiosis are identical to common species living free in nature. It seems that it must have been the fungal partner that hijacked the algae into the collaboration to become lichen. The fungi obtain their carbohydrates from the algal, or blue-green bacterial, partner. The latter employ photosynthesis to manufacture carbohydrates in their cells, at the same time “fixing” atmospheric carbon dioxide. For their part, the fungi access mineral salts like phosphates that would not otherwise be available to the algae. They live on rainwater and dust. Working together, these two organisms produce a collaboration that is remarkably tough. No doubt lichens will outlast us all.

I have dwelt on lichens in this chapter because I believe that symbiosis is a telling metaphor for the way that scientists work in a national museum. There is a close relationship between scientist, curator and librarian. Like the “algal” partner in lichen, all three are capable of independent existence. But working together in the Museum environment, the different virtues of all three partners produce something greater than any individual could on his or her own. The scientist might have the kind of manic devotion to research I have already described several times, but without a great library the work might not have the depth that makes a classic; the curator for his part is vital in ensuring that the contribution is there for posterity, and for other students. The collections and the work upon them should last like a crusty old lichen on a storm-blasted rock. Recall Sir Hans Sloane’s voyage to Jamaica in 1687. The specimens are still safely curated.

Molecules also confirm that fungi are not plants. The old classification on which the museum collections were organized lumped all the Crypts together. Now that the molecular trees have helped us peer into the deepest parts of evolutionary history, we can understand that the fungi split off from all the rest of living things very early in the history of the planet, perhaps as long as two billion years ago—the exact date is still the subject of dispute. As a whole, fungi are closer to the protozoan line that leads to animals than they are to the branch that leads to algae and, ultimately, to ferns and flowers. Lichen is therefore a collaboration between two kinds of organisms destined to have completely separate trajectories through Earth’s long history.

It is a little ironic that the fungi left their animal (second) cousins at the Natural History Museum and went to join the higher plants at Kew Gardens, while their symbiotic partners stayed behind. This divorce of natural partners was a consequence of the Morton Agreement of 1961, so called because Sir Wilfred Morton was then the chair of Trustees. The Agreement sought to divide out the taxonomic responsibilities of the sister institutions—no point in duplicating research, or so the argument ran. The world was actually carved up into fiefdoms. For example, according to the official document, the BM would have “Northwest Africa from the Atlantic Islands to Tunisia; S. Tomé and other W. African islands, excluding Fernando Po,” whereas Kew might have the “rest of Africa including Madagascar and Mascarene Islands.” South America belonged to Kew, while the arctic areas and Britain belonged to South Kensington. It did seem rather proscriptive, to say the least. But it worked in a kind of ramshackle, compromised way, even if it did separate the two halves of the lichen. The British responsibility at the BM also resulted in some major achievements, such as
The Island of Mull: A Survey of the Environment and Vegetation
(1978), which probably remains the most thorough survey of any biologically rich area of the British Isles, at 5,280 species, no less—including the fungi, despite the limitations of the Morton Agreement. Mull now has several nature reserves, and, being on the wet west, is full of lichens.

The Crypts also helped to save the United Kingdom during the Second World War. At the outbreak of war there was a curator of “seaweeds”—marine algae—called Geoffrey Tandy. He had come to the Natural History Museum from the BBC. He had a wonderful voice, and was a close confidant of T. S. Eliot; he it was who made the first ever broadcast of
Old Possum’s Book of Practical Cats.
According to his successor, Tandy was a competent taxonomist and contributed many herbarium sheets to the collections, which are still referred to today. However, he was not much of a publisher, and wrote only two scientific papers while at the Museum, a deficiency that eventually led to him being called before the Trustees; he excused himself on the ground that “writing up” was not part of his job description. He apparently ran two families in tandem, from which one son on the illegitimate side survives. The reason he saved the country—possibly even the world—from Nazism was because he was a cryptogamist. Evidently, a functionary in the Ministry of War had never heard of cryptogams, and thought that Tandy must have been an expert in cryptograms (that one extra letter ensures that the words appear next to one another in the dictionary). He was recruited to Bletchley Park—centre of signals intelligence during the war—because of his alleged talent in solving messages written in code. He had to work alongside the great brains that were tackling the mysteries of the Enigma Code—the only seaweed man among the ranks of cryptographers. It was a most fortunate screw-up. When sodden notebooks written in code were recovered from German U-boats, they seemed beyond recovery. However, Geoffrey Tandy knew exactly what to do. The problem was actually not so different from preserving marine algae. The Museum supplied the appropriate absorbent paper, and the pages covered in cryptic language were saved from soggy obscurity. The code was cracked, thanks to the fact that the word Linnaeus used for organisms reproducing by spores was but one letter different from the word describing messages written in code. One thinks of James Thomson (“The Seasons,” 1730): “A lucky chance that oft decides the fate / of mighty monarchs.” Or dictators.

We seem to have arrived once more back with Linnaeus. Since binomials given by Linnaeus represent the standard for plant names, it is obviously important to know exactly what they mean, both to understand how Linnaeus looked at the natural world and to fix the species in nature to which his names refer. It may seem strange that this still needs to be done, three centuries after Linnaeus’ birth. However, botany, like other disciplines, grew up haphazardly. There was plenty of opportunity for muddle and confusion. Although material was exchanged between scientists, this did not happen as widely as it does today. Because many parts of the world were being explored for the first time, the circulation of illustrations was often all that was done to make new discoveries known to waiting European savants. Foreign travel was difficult and expensive, so that scientists in the eighteenth and nineteenth centuries could not just pop over from Germany to consult the Sloane collection without the help of some serious patronage. A few of them were privately rich. Illustrations were often superb, but equally they could be inadequate and sketchy. Nor did Linnaeus necessarily have a specimen to hand when he coined a name. He often referred to illustrations in older floral works and simply dubbed them with his binomial. This chapter takes its title from one early work,
Theatrum Botanicum, or, Theater of Plantes,
by John Parkinson (London, 1640), which seems an appropriate label because so many of the stories from the plantsmen are thoroughly theatrical. I have already mentioned publications by Brunfels, Fuchs and Sloane, but there were many more. I particularly like J. J. Dillenius’ 1732
Hortus Elthamiensis,
an account of the garden of Dr. Sherard in Eltham, Kent,
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because it combines a feeling of exoticism with the name of an archetypal London suburb. Linnaeus himself published
Hortus cliffortianus
(Amsterdam, 1737) with illustrations prepared by the incomparable G. D. Ehret. These publications, for all their splendour, exude a whiff of vanity publishing among the rich—“my garden is more exotic than your garden”—but they endure as works of art as much as science.