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. va r. 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, desicca ted 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 th in, papery peel. The vascular bundles together with the inner mesocarp, whi ch remained parenchymatous in R. aromatica and became sclerified in R. glab ra, was attached to the future stone in R. aromatica but detached from it i n 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-l ayered; one and two weeks after anthesis in R. glabra and R. aromatica, res pectively, it had become distinctively 4-layered, and the innermost layer h ad 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 c rystalliferous one were fully elongated and had begun to lignify. In both s pecies, the crystalliferous layer remained parenchymatous, did not elongate , and contained crystals. The similarities in ontogeny and anatomy of the p ericarp in these two species support the opinion that Lobadium should be ke pt as a subgenus within Rhus, rather than being elevated to the generic lev el. However, more taxa of Rhus need to be studied before the taxonomy of th e genus can be clarified.