Scientific Squeeze

plant presses victoria island

plant presses, field camp, Victoria Island (Roger Bull, Canadian Museum of Nature)

When people travel they remember their trip in different ways. Most of us have a camera, some make notes in a journal, while others make entries through social networking venues. If you are a botanical researcher you go one step further and mark your voyage of discovery with pressed plants. Images of the landscapes, copious notes, and the geographical coordinates are part of the collection process, but critical evidence is obtained by taking plants, arranging them between sheets of paper and placing them neatly into a tightly bound stack that squeezes the specimens into two dimensions.

The botanical experts at the Canadian Museum of Nature work on all sorts of plants. They work in the field to discover and document the plants that live in water, ice, dirt, on rocks and just about every kind of habitat imaginable. In general, plants include life forms that are as small as the point of a pin (for example, diatoms) or as tall as a house. And because they aren’t mobile like animals plants often live for generations in one place and are able to tell us a great deal about the past. For example, studying a record of plant life across vast areas over time can reveal the climate history of an area and indicate what changes lie ahead.

plant sheet preparation

pressed plants being mounted for permanent collection

So what does a plant field record look like?  For larger specimens (visible by eye . . . the ones we’ll talk about), like the flowering plants, mosses, and ferns, field work is done at a time when the best characters of the plant for identification can be seen (usually during summer). Samples are taken of the entire plant intact (roots, leaves, flowers) – minus the dirt – or representative parts for larger plants like trees and shrubs.  These are placed between a large sheet of newspaper, one or a few for each species from a single location. A collection of those sheets is spaced between layers of cardboard, which lets air move through the specimens for rapid drying.  This stack is book-ended by wooden slats that are the same size as the cardboard and paper, and the entire pile is cinched together with straps, providing even pressure that flattens all the plants. This is a plant press.

Macoun plant and label

plant collected by John Macoun (1880) (Canadian Museum of Nature photo)

Plant presses have been used by botanists for centuries to create dry, preserved specimens for safe transport to the laboratory and long term storage. With some final adjustments and fixing onto a new and heavier paper sheet (usually clean white paper without the daily news printed on it), a pressed plant will last for several hundred years. Have you ever made something that will last several hundred years? This sounds simple, but a team of botanists in the field can collect hundreds of these specimens and the work to preserve them for a scientific collection can take until the next field season (or longer!).

Each of these botanical sheets has the original collection data that makes them so valuable for future study. Any new information acquired about the specimen will also be added to the sheet, as well as to the associated digital record. The museum is full of this kind of scientific data that it lends out (via specimens or as digital data), and uses for study.

Botanists discover and study plant specimens throughout Canada and abroad and have a tradition of taking enough samples for their work and for some of their colleagues. So once they have sorted their lot, there are packages sent far and wide in a global exchange of science data. The newest kind of specimens associated with this work is DNA. For hundreds of years botanists have used plant structures to tell one species from another. They still do this today, and more and more are also using DNA. The plant DNA comes from sub-samples for each pressed plant (usually the leaves) placed into small plastic bags of silica gel for quick drying and optimal DNA results.

A major effort led by the Canadian Museum of Nature in collaboration with many experts, called the Flora of the Arctic, is to discover and make a record and description of all the plants in the Canadian Arctic, a place where plant presses, DNA samples and botanists are moved around by helicopter. This dedication to the natural world is a regular part of scientific work at a museum, and a major contribution to understanding the natural heritage of Canada.

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One Response to Scientific Squeeze

  1. Pingback: Our Science Was State-of-the-Art in the 1700s | Canadian Museum of Nature – Blog

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