An exhibition of ancient plant fossils and living fossil plants opens tomorrow at the National Botanic Gardens, writes Anthony King
The National Botanic Gardens will tomorrow open a door onto prehistoric times with Jurassic bark - the evolution of the Plant Kingdom, an exhibition that recreates lost worlds using live plant specimens and features an array of plant fossils.
"The exhibition is a joint one between the Geology Museum in Trinity College and ourselves," explains Dr Peter Wyse Jackson, Director of the Botanic Gardens. "It is a unique exhibition, bringing together some really ancient geological specimens and living representatives from the same groups."
His brother, Dr Patrick Wyse Jackson of TCD's geology department, is taking care of the fossil side of the exhibition. It will display a range of fossil plant material and focus on some particularly good Irish examples, he says.
The exhibition includes some of the earliest plants discovered, including Cooksonia from Tipperary, which dates from 420 million years ago. There is also a selection of fossils from the Carboniferous swamps that gave rise to the coalfields of Britain and Ireland, including some from the famous fossil locality of Kiltorcan in Kilkenny.
The clubmosses and horsetails of this time grew as trees and the intricate patterns on their trunks are clearly visible in the Trinity fossils. Alongside its fossil-entombed relatives, there is today's whisk fern (Psilotum), which has changed little in 300 million years.
The Age of Dinosaurs - the Mesozoic period - saw the rise of seed plants over the spore-producing ferns, clubmosses and horsetails of the Carboniferous swamps. In particular, conifers, cycads and ginkgo trees came to dominate as the Earth became drier.
The survivors of this ancient flora will be on view, explains Dr Peter Wyse Jackson, "plants like the Wollemi pine, the ginkgo tree, and monkey puzzles, which are descendants from very primitive plant groups".
The Wollemi pine and ginkgo were described from fossils and then unexpectedly discovered in the wild. Ginkgo only survived by chance in monastery gardens in China and a stand of Wollemi pine was discovered in Australia just a few years ago.
"We also have specimens of dawn redwood, another tree described from fossils and then discovered in the 1940s," he adds.
The picture-book tree of the Jurassic however is the cycad. With their stout trunk, palm-like leaves and enormous cones, they offered a likely brunch for huge dinosaurs like Brachiosaurus.
Today, most cycads survive in the tropics and many are rare and endangered, says Dr Peter Wyse Jackson. The Botanic Gardens have a particularly impressive collection, including Wood's cycad (Encephalartos woodii), a species now extinct in the wild.
"It was collected in South Africa in the 1890s, an offshoot of one of the last specimens in the wild," explains Peter.
Only male plants are known, but the Dublin specimen has never produced cones. "We will watch with interest because it is conceivable that it could be the only female plant."
By the end of the dinosaur era, the dominance of cycads and conifers was being challenged by the flowering plants. At this time plants were preserved by basalt flows in Antrim, and visitors will see fossils of cypress, pine, popular and giant redwood from there, says Wyse Jackson. There is also petrified wood from Arizona and Ireland.
Wyse Jackson says the exhibition will explain "how our present plant kingdom evolved from the earliest beginnings". He notes that the garden's plant beds were recently rearranged according to insights gained from DNA studies.
"We used to believe that the evolution of plants was more or less linear, going from primitive ones represented by conifers and cycads, up to flowering plants such as orchids and grasses." It is now understood that the distinct plant lines diverged at a very early stage, he says.
The exhibition, which is part of Irish Geology Week, opens tomorrow and runs until June 16th. For further information, see www.botanicgardens.ie