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Biodiversity Blog


Through the Herbarium Cabinet: a Student View of the Billie L. Turner Plant Resources Center

by Sarah Hunter

Sarah 2 web

This summer, through the ongoing haze of the COVID-19 global pandemic, I had the unique opportunity to explore the inner workings of the Billie L. Turner Plant Resources Center at UT. The Herbarium Curation Summer Graduate Fellowship program allowed me three months of hands-on training in the varied aspects of herbarium curation, including specimen mounting, databasing, imaging, and georeferencing, all while working beside Curator George Yatskievych and Assistant Curator Amber Horning. During my fellowship, I saw how specimens are moved around the herbarium, and also got to work closely on my own summer curation project. I had weekly training sessions with Amber and George, and tried my hand at nearly every step: from gluing and sewing plant specimens, to packing specimens for loan shipments.

The complexity of an herbarium may surprise you, as it constantly surprised me.

For example, when a specimen first comes into the herbarium, it is freshly dried from a plant press. This press sandwiches plant cuttings, newspaper, and cardboard together in order apply even pressure, turning a three-dimensional plant specimen into a two-dimensional specimen that can be displayed on a page. The cutting is then placed into an ultra-cold freezer at -60° C for a week. This will kill any insects still in the plant.

From that point, the collector identifies the cutting, creates and prints labels in preparation for mounting. When it’s time to mount a specimen, the curator uses a glue formulated for book-binding. This is important because it dries as a PVA plastic , a polyvinyl alcohol polymer that is somewhat flexible and will not support fungal growth. The curator mounts the specimen on acid-free paper and allows it to dry. During the subsequent step, the curator or herbarium assistant sews the specimen to reinforce where the plant material would naturally experience strain or catch and pull up from the paper. The final step is to cover the knots from the strapping stitches with gummed linen. This ensures they do not catch on the next plant specimen when stacked.

From there, the curator files the specimen into one of the large herbarium cabinets, which have shelves specifically made for the specimen sheets.  The cabinets are sealed to prevent insects from feeding on floral parts which they may find delicious even in their preserved state. If the curator finds it relevant, he or she will database a specimen. In this process, the curator attaches a barcode to the specimen sheet, making it easy to keep track of which entry goes with which physical specimen. Then, an herbarium assistant parses and transcribes the information on the label into various fields, which include things like collector name, date, locality, and scientific name. This information is then hosted online through a portal under TORCH, The Texas and Oklahoma Regional Consortium, which allows students and researchers to easily access the information when and where they need it. Once a specimen is mounted and databased, it may be imaged to accompany the online data. For this, an herbarium assistant creates a high-resolution digital photograph in a closed lightbox with a ruler and color-standards card. These ensure that the color and white point balance can be corrected with editing software later. This results in uniformity across specimen images, and allows users to accurately measure floral parts.

Geo-referencing is another important aspect of digitization, using the locality information on the specimen labels to approximate a latitude, longitude, and (when possible) elevation of the origin of the specimen. It is potentially one of the most time-consuming aspects of herbarium work, as it can amount to a detective hunt for an obscure road or landmark. GeoLocate, an online set of tools from Tulane University, tries to triangulate a location based on the locality description. It also offers several types of maps and overlays, including historical maps, which can be helpful for older specimens and situations where the cities may have changed. An herbarium assistant adds the resulting data to the database, enhancing what researchers can learn about the specimens. With these data, researchers can conduct large scale analyses on the plants in a given area, as well as plant distribution studies. The information is even useful when examining when invasive species were introduced to an area, as many of the specimens are historical.

A. zenobiae web
 Allium zenobiae

Beyond specimen intake, storage, and databasing, the herbarium also loans specimens to other institutions. The herbarium normally loans specimens for a period of two years, but allows renewals for more time. The specimen uses are numerous, including taxonomic projects (such as identification and new species studies), and (when permission has been granted) sampling of tissue fragments for genetic or chemical studies.

In addition to my curatorial training, I worked on a project that stretched my taxonomic understanding. The Texan specimens of Allium canadense L. were muddled, and needed to be identified and reannotated. Allium is the genus of plants that includes onions, garlic, leeks, and chives, and its members have that hallmark “onion” smell. When I first approached this project, I had done very little taxonomic work, and faced a sharp learning curve. I read descriptions, looked at example specimens, and compiled a spreadsheet of variety characteristics. I also utilized several tools, such as georeferencing to determine the ranges of these varieties over the years, along with finding digital examples of specimens from other herbaria through TORCH.

While doing this, I realized the nuance that taxonomy requires, as the six main A. canadense varieties include intermediate varieties that have developed off of two main forms, Allium canadense L. var. fraseri Ownbey and Allium canadense L. var. mobilense (Regel) Ownbey. A. canadense L. var. fraseri Ownbey is a robust plant with uniformly white flowers, while var. mobilense is commonly petite, pink, and has pedicels (which attaches the flower to the stem) that are so slender they are almost thread-like. The resulting intermediate varieties fluctuate between the two forms, each with unique soil and habitat ranges. The asexual forms of these varieties are classified together into Allium canadense L. var. canadense, and are characterized by producing bulbils along with, or completely instead of, flowers. This struck me as odd, as it means that A. canadense L. var. canadense runs nearly the full gamut in terms of size, color, and habitat range. In short, it almost feels like a junk drawer for the asexual alliums, instead of classifying them according to their own lineages.

One of the most interesting parts of this project was a species description I found. Victor L. Cory, a  Botanist and plant taxonomist who worked on the flora of Texas, wrote this description, and it heralded a new wild onion called Allium zenobiae, which he refers to as the Queen of the Onions, due to its unprecedently large size and vibrant purple flowers. Previously, these specimens would have been included in var. mobilense, but Cory contended that the massive size difference (twice as stout, twice as tall, and a 6cm umbel, or floral head), and its later bloom time merited entirely separate consideration. I kept this in mind, and while sorting my way through the pungent herbarium sheets, I found a small handful of specimens that just did not fit var. mobilense. They were undoubtedly larger than the other mobilense, with vibrant lilac and purple colors that hadn’t faded, despite some being as old as sixty years. Many of the previous taxonomists had even written “unusually large” or “unusually robust” beside their determinations, indicating that I was not the first person to be struck by the large difference (pardon the pun). As a result of this project, the herbarium now has a newly identified species of Allium with several specimens to show for it.

Overall, this summer afforded me a rare look behind-the-scenes at the Billie L. Turner Plant Resources Center. I began the summer with basic taxonomic knowledge, and by the end of the season I had developed the skills and appreciation to see taxonomy from a much more complex point of view. Previously, I had spent time doing databasing work at the Mercer Herbarium as part of a larger internship with the Mercer Botanical Center in Houston. Because of this past experience in herbaria, I was greatly anticipating seeing and exploring the inner workings of herbaria in more detail. I highly enjoyed my time in the quiet maze of cabinetry and the training that I received has career applications beyond this summer, as I now have confidence with the basics of herbarium curation. I have always enjoyed the idea of herbaria, but spending the summer learning the tools and resources to know where to start when curating a herbarium collection has opened another possibility on my career path.

To see herbarium specimens from the TEX and LL collection, as well as plants from other collections from Texas and around the county, please visit https://portal.torcherbaria.org/portal/index.php.

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