Xylaria: Preserving Wood

Henry specimen box sm

Augustine Henry specimen box at the National Botanic Gardens of Ireland, photo by MCF

Among the herbaria I’ve visited, one of my favorites is in the National Botanic Gardens of Ireland at Glasnevin in the Dublin suburbs. There’s obviously some chauvinism here, because my mother visited the gardens as a high school student. Incidentally, she was a winner of the All Ireland Prize in Botany, and to prove it, my family has a massive document with Gaelic on one side and English on the other. But my love of the herbarium is based more on several jewels it houses, including specimens collected by Augustine Henry (1857-1930), a legendary plant hunter who had a long career as a physician with the Imperial Maritime Customs Service in China. His job seems to have been an excuse to get him to places where he could explore exotic flora, and he sent back 150,000 specimens to Kew, with some duplicates ending up at Glasnevin. His specimens included 25 new plant genera and over 500 new species. Henry is also known for giving the plant collector Edward Wilson directions on where to find Davidia involucrata, the handkerchief tree, which had been originally discovered by a French missionary, Armand David; in the Irish National Herbarium there is a specimen of Davidia that Henry himself collected.

But this was hardly Henry’s only connection with trees. After returning from China, he collaborated with Henry Elwes in collecting material for and then writing the seven-volume The Trees of Britain and Ireland (1906-1913). Elwes was a wealthy landowner with a passion for botany, and for trees in particular. To prepare this massive work the two traveled all over the British Isles in Elwes’s automobile, a daring feat at the time. They took photos, collected specimens, and then had illustrations made from these materials. The specimens are now at Glasnevin as the Augustine Henry Forestry Herbarium having been curated and then donated by his widow, Alice . After Henry died, she organized the 10,000 specimens collected for the project and chose to store the bulkier items like cones in the type of boxes used in clothing stores at that time. This was an ingenious solution to storage in the days before the manufacture of boxes specifically for herbarium specimens and before plastic bags were invented. The boxes, and the specimens, have held up very well. Each box is beautifully labeled as to its contents, and each has a cord around it so that it can be easily removed from the shelf. It is a thing of beauty to see rows of these lined up in compact shelving (see photo above). Another thing of beauty is the climate-controlled room where the treasures of the Glasnevin botanical library are stored. Here is more Henry material, including his heavily annotated copy of Trees; it shows how rigorously he corrected errors and added new information, including clippings of journal and newspaper articles.

Though I chose to begin a series of posts on xylaria with Henry’s material, technically these are not part of Glasnevin’s xylarium of about 1000 specimens. For the uninitiated, a xylarium is a collection of wood specimens, usually relatively small blocks of wood, that are used in identification of unknown wood samples as well as in other research. The Royal Botanic Gardens, Kew maintains an Index Xylariorum, sort of an Index Herbariorum for wood collections. The former is now in its fourth edition. There are about a million wood specimens in such collections worldwide with the largest at the USDA Forest Products Laboratory in Madison, Wisconsin with about 105,000 specimens including collections that were originally at the Yale School of Forestry and the Field Museum in Chicago. Another major xylarium, at Duke University, was sent to the du Pont Winterthur Museum.

These shifts were made in the mid-20th century and suggest that some institutions became less interested in wood collections than in the past. William L. Stern decried this trend as far back as 1973, and in 1976 described the history of the largest xylaria in the United States, including those I’ve just mentioned along with the ones at the Smithsonian, Harvard University, and SUNY College of Environmental Science and Forestry. Most of these collections were begun in the early 20th century, and they include microscope slides of thin sections of wood used in the study of wood anatomy. This was an area of focus in many xylaria for several decades, but then interest faded. This is one reason for the amalgamation of collections, along with the fact that wood specimens take up a great deal of room and like all other natural history collections, require active curation. One xylarium that has remained active from the 19th century on is at Kew. At one time, two of the four economic botany exhibits there dealt with wood and the xylarium remains a lively place.

Xylaria serve a number of purposes including studies in wood anatomy that I’ve already mentioned, and most prominently the identification of unknown woods, which can be everything from someone’s dining room table to objects from illegal trade in rare woods. Because of the economic significance of the wood industry, many governments especially in developing countries have set up xylaria over the past few decades, so while their use seems to be declining in the developed world, the number of xylaria overall is increasing. Forensic specialists also consult xylaria for criminal investigations, and archaeologists use them to identify the species found in wooden objects or structures. Wood specimens are particularly helpful in identification when they are vouchered, that is, when the specimen is linked to an herbarium specimen derived from the same tree; this makes identification much more trustworthy. Index Xylarium notes the percentage of vouchered specimens in each collection, and it varies from zero to almost 100%.

Stern makes two interesting and seemingly contrary points about the process of wood identification. He sees it as less pleasurable than identifying a plant from an herbarium specimen: “A wood specimen, at best, is only a fragment of an organism” (1973, p. 79). He finds the process nothing more than a necessary part of working in a xylarium and much prefers wood microanatomy, which involves an even smaller fragment, but includes the pleasure of microscopic examination. However, in another article (1976) he ends with an admission that one of the reasons for studying wood is aesthetic: so many woods are simply beautiful to look at. This aspect of wood collections should become clear in my next post on xylotheques.

Note: I am grateful to Dr. Matthew Jebb, Director of the Irish National Botanic Gardens, Glasnevin, for showing me its herbarium and library, and introducing me to the Augustine Henry material held there.

References

Elwes, H. J., & Henry, A. H. (1906-1913). The Trees of Great Britain and Ireland (Vol. 1–7). Edinburgh, UK: Elwes & Henry.

Stern, W. L. (1973). The wood collection–what should be its future. Arnoldia, 33, 67–80.

Stern, W. L. (1976). Multiple uses of institutional wood collections. Curator, 19, 165–170.

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