Plane Tree Family
This family is composed of large deciduous trees with erect trunks with smooth bark exfoliating in spots to give a mosaic appearance. Twigs have bud hidden by the base of the swollen petiole and often bear simple and compound hairs. The leaves are simple, alternate with 3, 5, or 7 palmate lobes. Petioles flanked by sheathing stipules. Leaf bases are cordate, truncate or cuneate and the basal surface is tomentose with stellate hairs becoming glabrous with age. The flowers are unisexual and axillary or solitary crowded into dense heads. Male flowers are sessile with 1 – 5 globose heads that soon fall off. Female flowers are sessile or stalked, terminal with 1 -7 gloose heads in pendulous racemes. Individual flowers are minute with 3 or 4 (tri- or tetramerous) parts. Sepals are free or fused at the base and the petals vestigial. Male flowers have 3 -4 stamens; female flowers have 3 -8 superior carpels. Fruits are achenes densely crowded in a head each achene surrounded by numerous hairs that are basally attached. Flowers are wind-pollinated and seeds wind-spread. The family occurs in North America from Canada to centrl Mexico. The family comprises just one genus, Platanus. The wood of these trees is resistant to splitting and is therefore used to make buttons and butcher blocks. Platanus comes from the classical Greek name for Platanus orientalis, ‘platos’.