Pericarp ontogeny and anatomy in Rhus aromatica Ait. and R-glabra L-(Anacardiaceae)

Ontogeny and anatomy of the pericarp were studied in Rhus aromatica Ait. var. aromatics of subgenus Lobadium and in R. glabra L. of subgenus Rhus. The exocarp sensu stricto in both species originated from the outer epidermis of the ovary wall and remained single-layered. However in a mature, desiccated fruit, the exocarp was united with the outer mesocarp, and this united-layer was physically detached from the rest of the fruit, thus forming a thin, papery peel. The vascular bundles together with the inner mesocarp, which remained parenchymatous in R. aromatica and became sclerified in R. glabra, was attached to the future stone in R. aromatica but detached from it in R. glabra. The endocarp sensu stricto of both species originated from the inner epidermis of the ovary wall. At anthesis, the proto-endocarp was 3-layered; one and two weeks after anthesis in R. glabra and R. aromatica, respectively, it had become distinctively 4-layered, and the innermost layer had elongated 5-10 times. Five weeks after anthesis in R. aromatica but only three weeks after anthesis in R. glabra, all layers except the outermost crystalliferous one were fully elongated and had begun to lignify. In both species, the crystalliferous layer remained parenchymatous, did not elongate, and contained crystals. The similarities in ontogeny and anatomy of the pericarp in these two species support the opinion that Lobadium should be kept as a subgenus within Rhus, rather than being elevated to the generic level. However, more taxa of Rhus need to be studied before the taxonomy of the genus can be clarified.