Research Expertise: Botany

Diatoms are one-celled protists, which by definition are neither plants nor animals. Like plants, diatoms contain chlorophyll and produce their own energy, so they can be studied under the field of botany.

Diatoms are encased in a silica shell that is like a shoebox with a bottom and a slightly larger top. Silica is the hard mineral substance silicon dioxide, and is widely used in the manufacture of glass.

You are looking at artwork made with the shells (valves) of several diatoms. In this form of art, diatoms are arranged in an attractive pattern by a patient microscopist. The traditional tool for collecting the shells are eyelashes (especially pig eyelashes) because the shells will stick to their oily tips. The diatom shell becomes free from the eyelash when placed into the stickier mounting material on the microscope slide. The challenge for the microscopist is to carefully place the shells in the correct pattern. A mistake is usually difficult to correct.

After the diatoms are mounted onto the microscope slide they can be examined with a standard microscope using black field optics. Black field optics present the sample like a negative, with the light background appearing black and the solid silica shell appearing white. Refraction of light through their silica shells also makes the diatoms appear different colours. The amount of the light's refraction and therefore, the resulting colour, depends on the thickness of the diatom.