XVI International Botanical Congess
We surveyed leaf crystals in Prunus (Rosaceae, 150-200 sp., five subgenera) and charted their patterns during seasonal leaf development in P. virginiana (Padus). Druses are most common, but prismatics predominate in subgen. Laurocerasus and Padus. Leaves removed from buds and stem tips were mounted whole. Scales abound with prismatics, transitional leaves have fewer crystals. Stipules teem with prismatics. Youngest leaves have 4-6 prismatics at apex, none elsewhere. At about 1.2 cm leaf length, dot-like prismatics appear throughout lamina except around veins, the crystals enlarge and smaller ones appear in between them as lamina expands. Tiny druses appear in midvein base at about 1.5 cm leaf length, with growth, druses form acropetally and, later, outward in main lateral veins, but never in mesophyll.