Subepidermal idioblasts and crystal macropattern in leaves of Ticodendron (Ticodendraceae)

Abstract

Previously unknown leaf anatomy and foliar crystal macropattern are described for Ticodendron incognitum Gomez-Laurito and Gomez P. (monotypic eudicot family Ticodendraceae of a Fagales subclade with Betulaceae and Casuarinaceae). Leaf samples of five herbarium specimens were rehydrated, bleached, dehydrated to 100% ethanol, then xylol, mounted in Permount and viewed using polarizing microscopy. Large adaxial and abaxial hypodermal idioblasts occur. Numerous small druses populate palisade mesophyll, and fewer, larger druses populate the spongy mesophyll; this is the opposite of druse distribution in Fagaceae. Druses dominate major veins, many with visible cores, and some prisms occur. Minor veins exhibit isolated groups of 1–8 druses and rare prisms, but most terminal veins lack crystals. Many druses are misshapen or with epitactic crystals; several unusual variants of druses and prisms are common. Hypodermal idioblasts are an apomorphy for Ticodendraceae, but oil and resin cells occur in Myricaceae and Rhoipteleaceae of Fagales. Crystal forms and distribution differ from known Fagalean macropatterns.