Greek ostryos—scale, in reference to scaly catkins.

Deciduous trees. Bark rough, scaly. Buds pointed. Leaves alternate, more or les ovate, long-pointed, marginal teeth often with short points, vein pairs mostly 9-15. Flowers unisexual. Male catkins pendulous, perianth segments absent, stamens 5-15 with bracts. Female flowers with 2 flowers in the axil of each bract, the sepals surrounding the ovary; bracts forming a tubular sheath. Fruit a ribbed nut enclosed within the bracts.

Seed.

Bracts forming a balloon like bag or sheath.

9 species from temperate N America and Eurasia.

Rushforth (1987).

Source: Spencer, R. (1997). Betulaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.