sentences:  'Thomson' is distinguished by a single trunk bearing a vase-shaped crown, the branches forming strong wide-angled crotches; the bark is dark grey and deeply fissured.The twigs have diamond-shaped fissures that become more apparent on second-year wood, and occasionally sport corky wings.The leaves are borne on 1 cm petioles, and average 7.5 cm in length, obovate to elliptic, with the typical acuminate apex and oblique base; dark green and glabrous, they turn bright yellow in autumn.