| BEN |
| BOTANICAL ELECTRONIC NEWS |
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| ISSN 1188-603X |
| No. 308 April 16, 2003 | aceska@victoria.tc.ca | Victoria, B.C. |
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Alec Stokes, diffident, neglected but central author of the revolutionary work that revealed the double helix structure of DNA, published in Nature April 25, 1953, has died nearly 50 years later.
Stokes was born June 27, 1919. He was educated at Cheadle Hulme School in Manchester and Trinity College, Cambridge. He did his doctoral research at the Cavendish Laboratory in Cambridge.
During the critical period of research into the structure of DNA, Stokes was a mathematical physicist at the Wheatstone Physics Laboratory at King's College London, which he had joined in 1947. Maurice Wilkins also worked there, and Stokes co-authored with Wilkins and Herbert Wilson, the Nature paper that followed Francis Crick and James Watson's, and gave X-ray evidence for the helical structure Crick and Watson had proposed. The paper by Rosalind Franklin and Raymond Gosling (with much clearer pictures) notoriously came third.
Herbert Wilson told The Scientist how important Stokes' contribution had been: "He worked out the theory. When Wilkins and Gosling got the first good diffraction patterns in 1950 they showed them to Alec Stokes, and he saw straight away that they could be explained on the basis of a helix. Then he worked out the theory going home on the train, very very quickly."
"I was very impressed with his ability," said Wilson. "In fact, before I went to King's I had worked on the solid state, on the effect of cold work on metals, and Stokes had made important contributions there too. He was exceptionally good mathematically."
X-ray diffraction pictures of crystals are effectively mathematical transformations of the pattern of the crystal into another pattern the X-ray picture. Stokes calculated that for helical crystal components this should be a particular combination of "Bessel functions," which arise in situations of cylindrical symmetry. The mathematics provided the logic that enabled the exact interpretation of the X-ray pictures of the DNA fibres being studied at King's, giving the helical structure and ladder spacing.
"I joined King's in September 1952, and stayed until 1957," said Wilson. "When I first went for interview I was introduced to Stokes and Rosalind Franklin. He was a very pleasant person, so modest."
"When I started I was comparing DNAs from different sources" said Wilson. "The good one that Wilkins and Gosling had looked at first, and got good patterns from, was from calf thymus. And the question was, were they the same from all sources? We showed that they were similar."
But Stokes was so modest that he never published his Bessel function theory, said Wilson. Instead, William Cochran, Francis Crick and Vladimir Vand published essentially the same argument in Acta Crystallographa in 1952, acknowledging that the same theory "was also derived independently and almost simultaneously by Dr A.R. Stokes." In her biography, "Rosalind Franklin: The Dark Lady of DNA," Brenda Maddox said, "Stokes, still reluctant to publish his own helical work at King's, declined to be cited more directly."
Herbert Wilson told The Scientist, "I asked him why I think he was hoping for more proof, that a model would appear a model of DNA so he could test the theory". Which, of course, then took place but in Cambridge, not at King's.
According to Maddox, "Stokes much preferred theory to fumbling with cameras and messy gels," but he got on well with Rosalind Franklin, who focused on perfecting the X-ray techniques. Wilkins mentioned both in his Nobel address, saying she and Stokes "made very valuable contributions to the X-ray analysis." With typical modesty, Stokes said of the Nobel Prize awarded to Crick, Watson and Wilkins in 1962 that perhaps he deserved a 5000th part of it.
Remaining at King's in the 1950s and 1960s, Stokes continued to work on large biological molecules. He published the book "The Theory of the Optical Properties of Inhomogeneous Materials" in 1963, dealing with molecules in solution, and "The Principles of Atomic and Nuclear Physics" in1972. He retired from King's in 1982.
Stokes died February 5, 2003. His wife, Margaret, two sons and a daughter survive him.
Nova Scotia's coastal plain flora is a group of about 50 species of plants restricted to the southern part of the province and disjunct from a more continuous range on the Atlantic coastal plain of the United States. Forty-one of the species are threatened in Nova Scotia and this unusual flora is a biodiversity protection issue that has attracted much attention in eastern Canada (http://conservation.acadiau.ca/coastalplainflora/about.htm). Some infraspecific variants and genotypes of more widespread species also have the restricted coastal plain pattern. The recent discovery of the typical coastal plain variety of Proserpinaca palustris L. in southern Nova Scotia provides an example. In 1935 Fernald and Griscom separated the northern variant of Proserpinaca palustris L. with "more elongate fruits 2.3 - 4 mm broad with subacute angles" as P. palustris var. creba Fernald and Griscom. The more southern, typical variety was noted to have "broad and thin- angled concave-sided fruits 4 - 6 mm broad." Both of these varieties were distinguished P. palustris var. amblyogona Fernald of the interior from P. palustris which has the angles of the fruit strongly rounded. It was noted that many of the plants from the coastal plain area from New Jersey to Nova Scotia were transitional between P. palustris var. palustris and P. palustris var. creba. Fernald's overlapping variety concept was not popular in later years, but it remains of interest for two reasons. Firstly, many of his varieties have been found to be very distinct and discontinuous including some that he himself abandoned. Secondly, even in cases where the extent of overlap makes varietal rank unwarranted, the named taxa are often associated with an interesting and distinctive pattern of geographic variation that relates to both genetic structure and evolution. The distinction of P. palustris var. creba and P. palustris var. palustris is of interest for both of these reasons. The varieties of Proserpinaca palustris recognized by Fernald (1950) have been employed by some recent authors (e.g. Gleason and Cronquist 1991, Catling 1998) but not by others (e.g. Crow and Hellquist 2000). A distinct geographic pattern was recently revealed in the southeastern US plants based on examination of 1400 specimens (Catling 1998): the P. palustris var. palustris was largely confined to the Gulf and Atlantic coastal plains, P. palustris var. amblyogona Fernald occurred only in the Mississippi embayment area, and P. palustris var. creba occurred throughout the southeast. Whether or not one chooses to recognize varieties, there is a distinctive geographic pattern of morphological variation at least in the southeastern US. This pattern also extends northward with P. palustris var. palustris being largely confined to the Atlantic coastal plain north to Massachusetts and P. palustris var. creba being widespread (Fernald 1950, Gleason and Cronquist 1991).
Although both Boivin (1966) and Scoggan (1979) listed P. palustris var. palustris, it is clear that they included P. palustris var. creba with it on the basis of the wide range reported. It appears that the material they examined is referable to P. palustris var. creba. Fifty- five specimens of Proserpinaca palustris at the AAFC vascular plant herbarium (DAO), from Nova Scotia, Quebec and Ontario, are all referable to P. palustris var. creba, with the exception of a few from the Georgian Bay region of Ontario that may be better placed with (the less well defined) P. palustris var. amblyogona. A few from extreme southwestern Ontario appear transitional between P. palustris var. creba and P. palustris var. palustris, but no specimens are clearly referable to the southern coastal plain P. palustris var. palustris.
With regard to Nova Scotia, Roland and Smith (1969) and Zinck (1998) referred the Nova Scotian plants to P. palustris var. creba, probably on the basis of Fernald's reported range (Fernald & Griscom 1935, Fernald 1950). Fernald was an expert on the flora of Nova Scotia and his reports were thus unlikely to have been questioned. It was a surprise then to find among specimens sent from the New York Botanical Garden (NY), two sheets of material collected in Nova Scotia that were referable to P. palustris var. palustris.
NOVA SCOTIA: Lunenburg Co.: thickets bordering peaty swale bordering Rhodeniser Lake, east of Bridgewater, 18 August 1921, M. L. Fernald and B. Long 24227 (NY); Yarmouth Co.: boggy savannah by Butler's (Gravelton) Lake, Gravelton, 4 Sept. 1920, M. L. Fernald, B. Long and D. H. Linder 22026 (NY).
The plants from near Bridgewater have immature fruit to 4 mm across and narrow wings 1.0 mm wide. The plants from Gravelton have fruit with very thin wings 0.5-0.8 mm wide, concave sides and are up to 4.5 mm wide. Both of these specimens were determined by Fernald as P. palustris var. creba in 1934, but they clearly approach P. palustris var. palustris more closely than a specimen ( bog W of the railway station, Bennett, New Jersey, 29 Aug. 1922, J.M. Fogg jr. 199, NY) identified by Fernald as the P. palustris var. palustris in 1941. Both the Gravelton and Bridgewater specimens also correspond to many specimens at NY from Bermuda, Cuba and Bahamas (Brown & Britton 338, Britton and Brace 513, Britton and Cowell 9678) annotated by N. C. Fassett to P. palustris var. palustris in 1953. The Nova Scotia specimens also correspond to the Gray Herbarium Exsiccatae set 1457 (Virginia, Southampton Co., peaty margin of Whitefield Pond southwest of Corinth, 7 Sept. 1946, M. L. Fernald, B. Long, I. D. Clement, DAO). Finally the Nova Scotia specimens are referable to P. palustris var. palustris in various keys (e.g. Fassett 1940, Fernald 1950, Catling 1998). It stands to reason that if P. palustris var. palustris, a coastal plain taxon, was going to occur anywhere in Canada, it would be in southwestern Nova Scotia where many coastal plain species are disjunct including its close relative, Proserpinaca pectinata Lam. The occurrence of Proserpinaca palustris var. palustris sensu stricto in southern Nova Scotia is a signal to the possibility that along with very distinctive species disjuncts in southern Nova Scotia, there may also reside very restricted (in Canada at least) infraspecific variants of more widespread species. Since protection of biodiversity should operate at the infraspecific level, as well as at higher levels, such variants deserve protection along with the rest of the coastal plain flora.
References
Good news. At a meeting in Corvallis on April 12, 2003, the Oregon Natural Heritage Information Center (http://www.oregonstate.edu/orhnhic/) agreed to raise Sidalcea hendersonii S. Watson from List 2 to List 1 (Endangered or threatened throughout its range), and its global rank to G3 (Rare, Threatened or Uncommon throughout its range).
The US Fish and Wildlife Service has indicated it will give Sidalcea hendersonii "Species of Concern" protection following this summer's field surveys if we document that it is as rare in Oregon as we fear.
See the coming May Native Plant Society of Oregon Bulletin for an article on our efforts.
For those of you planning surveys this summer: if you discover populations of Henderson's checkermallow, please measure or estimate area covered by the plant and count or estimate number of plants present. (Since one large plant may produce many flowering stems, be sure you do not overestimate number of plants.) And please assess threats. Also useful would be estimates of the percentages of female- only plants vs. perfectflowered plants. If you can, take along a vial and collect any weevils you may find on flowers or capsules. (Weevils can be sent to Steve Gisler, Botany Dept., Cordley Hall, OSU, Corval lis, OR.)
[Note: For weevils on Sidalcea hendersonii in British Columbia see BEN # 215, February 21, 1999]
Starting in 1934, Glacier Lake, off the upper South Nahanni River in Canada's North West Territories, became the focus of intense Canadian and American scientific interest.
The Mackenzie Mountains were one of the last big biological and geological blank spots on the continent. The American Museum, working with the National Museum of Canada, and funded by American Museum patron Colonel Harry Michener Snyder, mounted a large expedition in 1937. George Goodwin, Assistant Curator of Mammals at the American Museum, and Howard Frederick Lambart of the Canadian Geological Survey, were the leading scientists.
In 1939, Harvard University sent in biologist Hugh Miller Raup, Raup's wife Lucy (a lichenologist), and Jim Soper (a graduate student from McMaster University).
In 1952, as the Cold War got hot, the Pentagon wanted to find out how to correlate ground features with RCAF aerial photos, and sent in Dick Shamp (air photo interpreter), Norm Thomas (professional photographer) and Howell Martyn (biology student). Also that year, Snyder led another expedition to the lake, this one to collect large mammals for dioramas at the National Museum. The Canadian Wildlife Service sent biologist Donald Flook to help Snyder.
Flook returned for more studies the following year, and over the next couple of decades the CWS continued this work. Prominent among the officers involved was George W. Scotter, who did the work preparatory to the establishment of Nahanni National Park.
Diary of a Lake is an anthology of scientific writings about Glacier Lake, along with the articles for popular magazines and private journals and diaries produced by the scientists. The photographer on the Pentagon team was so impressed (or traumatized) by his experience that he produced a short story. Lucy Raup later published a camper's cookbook based on her years of studies in the Canadian north; Diary of a Lake includes some of her recipes that proved popular with the members of her group.
The expeditions also involved a lot of photography, and Diary of a Lake includes 25 historic photos as well as some new ones taken by the editors. Also there are maps. Lambart's job was to produce the first contour map of any area in the Mackenzies, and that map is reproduced here.
It all adds up to a complete and surprisingly unscientific, quite personal, look at an amazing piece of landscape, by people who went on to become figures of some importance in the scientific world. People like
George G. Goodwin, author of a great number of popular books on the world's great mammals, and of many of the entries on mammals in Collier's Encyclopaedia, 1950 - 1980.
Howard Frederick Lambart, author of studies of the Pacific Coast glaciers and accounts of topographical work around Mount Logan and the Rockies. Member of the 5-man team that first summated Mount Logan.
Hugh Miller Raup, one of North America's great plant geographers, responsible for plant maps of much of northern Canada. Raup's The Botany of Southwestern Mackenzie, based entirely on his work at Glacier Lake, is one of the classics of plant geography and is excerpted in Diary of a Lake.
Dick Shamp, leader of the Pentagon expedition of 1952, whose correlation of aerial and ground photos of the area may really have been a cover for uranium prospecting, who led his little group out far beyond the likelihood of a safe return.
Donald Flook, Wildlife officer assigned to keep an eye on the somewhat egotistical and erratic Col. Snyder during the second Snyder Expedition.
Diary of a Lake also includes a Foreword by David Raup, son of Hugh Miller and Lucy, who at six year of age "assisted" his parents through their work at Glacier Lake. David Raup became one of America's foremost palaeontologists, author of Extinction, Bad Genes or Bad Luck, The Nemesis Affair, Principles of Palaeontology, and other books.
Finally, there's an introduction by editor John Harris, author of Tungsten John about the legendary South Nahanni River, and an access guide by Vivien Lougheed, author of the Kluane National Park Hiking Guide, Forbidden Mountains (Tibet) and The Adventure Guide to Belize.
From: James Macklin [macklin@ACNATSCI.ORG], originally posted on Taxacom Discussion List [TAXACOM@USOBI.ORG]
We have made an interesting discovery here in the Herbarium of the Academy of Natural Sciences in Philadelphia and would like to further our knowledge through input from you. Many of you are aware of our past beetle problems and that we have recently completed an upgrade of our cabinetry and compactor system thanks largely to a BRC grant from NSF. For two years now we have been actively freezing our collection for a period of one week at -20 degrees C (we are about half done). We expected a carry over of some beetles into the new system since we have not frozen all the material. In the last few months we noticed larvae in cabinets where the plant material had been recently frozen. Through discussion with Entomologist colleagues we surmised that the larvae witnessed were likely a product of the thawing process which acts as a wake up call for eggs to hatch. Thus our first question to those in herbaria is have you witnessed this phenomenon in your collections? Next, have any of you tried a cycle of freezing, thawing and then refreezing, and if so, how many days in and out?
The story gets more interesting. We assumed that all the larvae we were seeing were from Cigarette beetles (Lasioderma serricornes) since the adult beetles appear on our traps and, based on what is known of their habits, these animals are implicated as the predominant if not exclusive pest in the herbarium. One of our curatorial assistants took a more careful look at these larvae and noticed that they did not look the same. Our Entomologists confirmed this and as it turns out the most common larvae are of the Odd beetle (Thylodrias contractus). So, our question to other knowledgeable herbarium managers and En tomologists out there is do these 'Odd' beetles like to eat plant material preferentially? The larvae certainly do a good job of devouring the dead Cigarette beetles. Does anyone know a good way to trap out these beetles? So far I have not been able to locate a pheromone lure for the Odd beetle.
Any information would be greatly appreciated.