Professor Dan Lewis: Botanist and scholar

While expanding the evening primrose work, he turned to the dung-heap toadstool, Coprinus lagopus. This fungus appeared to have a similar multi-gene breeding system that was easier to work with, did not need land for growing and enabled him to study mutation in a way that he could never have done with higher plants.

As a result of his basic studies on the mating system of the fungus, Coprinus has proved to be an excellent model organism for research on fungal genetics and is still used by groups around the world today.

Based on his direct experience of flowering plants and fungi, he published in 1954 an outstanding review Comparative Incompatibility in Angiosperms and Fungi. This review has since been declared a Citation Classic in two different series of Current Contents. The following year he was elected a Fellow of the Royal Society.

Dan Lewis was born at Basford, Stoke-on-Trent, in 1910. He was the second child of Edith and Ernest Lewis. Ernest had inherited the wholesale grocery business run by Dan’s grandfather (also Dan Lewis, whose first job was as “gentleman’s gardener” near Swansea).

Aged 9½, Dan Lewis was very excited to read that a British edition of The Boy Electrician by Alfred P. Morgan was to be published in July 1920. He persuaded the local bookseller to let him buy it a week early. This book, his prized possession, was permanently by his chair. It fuelled his enthusiasm for electricity so much that his teachers at Newcastle High School urged him to go to Cambridge to read physics.

However, while he was on a cycling tour, his brother contracted scarlet fever. Dan was sent to stay with a Mr Wooding, a pottery designer and enthusiastic gardener. There, he was introduced to horticulture and gradually changed his allegiance from physics to botany.

On leaving school Lewis had 2½ years’ practical horticultural experience before he read botany at the University of Reading. While an undergraduate he was married to Mary Phoebe Burry. She died four days after their 70th wedding anniversary.

Having proved his worth with his early publications, he was given complete freedom to work on the evening primrose. He found that on doubling the number of chromosomes in the plant the incompatibility broke down. Using the style as a highly sensitive selector of mutations in the pollen (induced by X-rays on pollen developing in buds), he showed the system to be controlled by at least two and probably three closely linked genes. One gene was active in the style, another in the pollen. He found that this process involved an immunological interaction in this species.

By X-raying cherry buds he successfully “crossed” two varieties that were not compatible. Any cherry produced should contain a mutation allowing self-fertility. More than 2,000 such cherries were planted to produce little trees. A political decision to stop work on cherries meant that the possible saviour of cherry growing in the UK was “thrown on the compost heap”. Fortunately, however, one of these selffertile “seedlings” was sent to a breeder in Canada, who crossed it with the North American variety Lambert. The result was the first self-compatible cherry variety Stella. Most garden centres now stock Stella.

He began studies on the biochemical genetics of methionine in Coprinus during tenure of a Rockefeller Fellowship at the California Institute of Technology (1955-56). While there, he was approached about the Quain Professorship at UCL. Several of the students he met in his early years at UCL have achieved great academic success in genetics. His teaching was marked by the infectious enthusiasm of the excellent research worker.

At the end of a visiting professorship to the University of Delhi, he and Phoebe drove their Triumph Herald from India to England.

There was a long-running programme of research at the JI on the two types of primrose, pin and thrum (distyly). Lewis’s physiological research on the system showed that the mechanism relied on an osmotic interaction between pollen and stigma and was therefore different from the evening primrose. Late in his career, he began studying the distylic maritime shrub Pemphis acidula, which he first saw during a visiting professorship to the University of Singapore.

To collect flowers for research he visited numerous exotic sites all round the Indian Ocean, including the atoll of Aldabra. The occurrence and frequencies of several different types of homostyles that he found in this plant have still to be explained. On one occasion in East Africa he and Phoebe were robbed at knifepoint.

For some years he was a valued member of the University Grants Committee, a trustee of the Royal Botanic Garden, Kew, president of the Genetical Society and member of the governing bodies of the leading plant research stations in England and Wales.

His retirement lasted 31 years. During that time he kept fit by swimming, pulling weights and tending a vegetable garden. Aged 80 he swam 5,000m in a charity event. In his youth he had played the clarinet, while his elder sister Dora was a more than competent pianist. His love of Mozart was well known; the recordings by Alfred Brendel and Murray Perahia cheering him up for several years after Phoebe died. The support of a remarkable carer, Esline Sibanda, enabled him to live in his own home until less than two weeks before his death.

Lewis is survived by his daughter.

Dan Lewis, FRS, Emeritus Quain Professor of Botany, was born on December 30, 1910. He died on September 30, 2009, aged 98