Morphological comparison of Populus gonggaensis with P. cathayana and P. lasiocarpa A male flower of P. cathayana (floral disc entire) B female flower of P. cathayana (floral disc entire, ovary glabrous) C male flower of P. lasiocarpa (floral disc parted) D female flower of P. lasiocarpa (floral disc parted, ovary pannose) E capsule of P. cathayana (floral disc persistent, pericarp glabrous) F capsule of P. lasiocarpa (floral disc deciduous, pericarp tomentose) G female flower of P. gonggaensis (floral disc parted, ovary partly pannose) H fruiting branch of P. cathayana (leaf abaxially glabrous, base rounded or subcordate) I leaf of P. lasiocarpa (base deeply cordate) J young leaf of P. lasiocarpa (abaxially tomentose) K young leaf of P. gonggaensis (abaxially glabrous, base subcordate).