Macropattern of styloid and druse crystals in Quillaja (Quillajaceae) bark and leaves

Quillaja has been shuffled among tribes and subfamilies of Rosaceae, segregated from it as a separate family, and, most recently, transferred to the Fabales as a separate family. Many anomalous characters have kept it from being settled anywhere permanently. One character never mentioned by systematists, but long known, is the anomalous (for Rosaceae) occurrence of prominent styloid calcium oxalate crystals, reported from the inner bark of stems. We describe in more detail the macropattern of crystal distribution in stem and leaf, using vibratome sections, sodium hypochlorite clearings of leaves, and polarizing and scanning electron microscopy. Styloids are extremely numerous in the phloem of stems, and they continue in phloem of the short petiole and midrib bundle and in main lateral veins of the leaf lamina. Druses, never reported before, occur in cortex and pith of young stems (not seen in old stems) and are numerous in the spongy mesophyll, but not the palisade mesophyll, of the leaf lamina. Styloids occur in three of the four families of the newly constituted Fabales. Styloids in phloem, along with fiber strands, may provide a barrier to protect from bark borers and similar pests.