A vocabulary of landscape — a landscape of words
1190 entries
diatom
A diatom is a single-celled alga that lives inside a glass box it builds for itself out of silica dissolved from the water. The box comes in two halves, one fitting over the other like a lid on a petri dish, and the surfaces are patterned with pores and ribs in an arrangement specific to the species. There are tens of thousands of species. They live in the ocean, in fresh water, in soil, and on wet rock.
Etymology
The name is Greek for cut in two, which describes the two-piece shell rather than anything the organism does. It was applied in the early nineteenth century, when the microscope had just made these things visible and naturalists were working out how to name a world nobody had seen. Older writing calls them Bacillariophyta, little-rod plants, which describes only the rod-shaped ones.
Notes
Diatoms carry out something like a fifth of all photosynthesis on the planet, so a substantial share of the oxygen in any breath came from them. Their glass shells sink and accumulate, and thick beds of the resulting rock are quarried as diatomaceous earth, used as a filter medium, an abrasive, and an insecticide. Victorian microscopists arranged individual diatoms into elaborate patterns on slides, moving them one at a time with a bristle.