Flora of North America species comparison

thin, close or exfoliating in thin sheets, becoming thicker and frequently furrowed or broken in age;

lenticels often present, prominent, sometimes becoming greatly expanded horizontally.;

bark and wood strongly tanniferous.

3-ranked, occasionally nearly 2-ranked.

perianth of 4(–6) sepals, well defined, minute, membranaceous.

2–3 per scale, scales arranged in conelike catkins;

perianth not obvious;

ovules with 1 integument.

1–4 cm, conelike, composed of many scales;

scales either persistent or deciduous with fruits, crowded, small, woody or leathery.

tiny samaras, lateral wings 2, membranous, sometimes reduced to ridges;

pericarp thin, leathery.

and branches terete.

twigs and buds often covered with small to large, resinous glands;

pith triangular in cross section.