Crystal diversity and macropatterns in leaves of Oleaceae

Oleaceae leaves surveyed from herbarium specimens of 240 species from 23 genera were rehydrated, bleached, processed into xylol, mounted unstained, and viewed microscopically between crossed polarizers. Occurrence of five crystal types and two variants (tiny acicular crystals and sphaerites) within one family is unusual. Number of crystal types within a single species was one (108 spp.), two (53 spp.), three (51 spp.), four (15 spp.), and five (6 spp.). Seven species lacked crystals. The tiny acicular crystal variant was most common (167 spp.), followed by prisms (67 spp.), raphides (65 spp.), druses (61 spp.), sphaerites variant (50 spp.), styloids (36 spp.), and crystal sand (21 spp.). Epidermal crystals were common (155 spp.), with epidermal crystals clustering at base of trichomes in 21 species. Jasminum was exceptional in having mostly druses and almost no crystals around vascular bundles. Most Oleaceae crystals are tiny, usually about 5 μm in length, except for larger styloids and raphides.