1992, Oliver Sacks, Migraine, Berkeley: University of California Press, revised and expanded edition, Part 5, Chapter 17, p. 279,
Sometimes these networks have an acicular or crystalline appearance, and may grow visibly, sometimes with sudden jerks, “like frost on a windowpane,” or “primitive plants.”
Having sharp points like needles.
(botany) Of a leaf, slender and pointed, needle-like.