When told that a herbarium is a collection of plants, most people think of flowering plants or pine trees, or perhaps even ferns. The herbarium possesses these plants, but it also has other plants – an often, overlooked group of plants, the bryophytes that include mosses, liverworts and hornworts.
Bryophytes are small. As a result, the characters that distinguish bryophytes are small, microscopically so, but the array of beauty and intricacy displayed in flowering plants also are present in bryophytes. Those researchers that study bryophytes, bryologists, are privileged to observe this vibrant world of miniature plants.
Bryophytes often grow in places where other plants cannot grow, such as on the sides of trees or on the surface of boulders. Bryophytes are able to grow on such substrates because they are able to survive after drying to conditions equal to the water content of the surrounding environment, conditions that would cause wilting and death in other plants. Poikilohydry, this ability to dry and then re-establish growth in the presence of moisture, is a character that flowering plants have evolutionarily lost. In herbaria, the poikilohydric nature of bryophytes has been observed in some specimens that are able to grow after five, ten or twenty years dried in a herbarium.
Bryophyte specimens are easier to collect and to preserve compared to other plants because they do not require pressing, or mounting onto herbarium sheets. While in the field, bryophyte plants are assigned a collection number and placed into small paper bags or paper envelopes, where they are dried. In the herbarium, bryophytes are stored in envelope packets that are made from 100% cotton rag archival paper. Labels with species identification, collection location, habitat information, collection date and collector are printed onto the face of the envelope. The envelopes are stored in flat boxes specially designed to fit on the shelves of herbarium cabinets.
The Ohio State University Herbarium contains over 10,000 specimens of bryophytes – a bryologist’s delight.
About the Author: Dr. Cynthia Dassler is Curator of Cryptogams (small plants that produce spores) at The Ohio State Herbarium (OS) in the Department of Evolution, Ecology and Organismal Biology.