Abstract
Carpinus gigabracteatus Z. Qiang Lu, a new hornbeam species from southeast Yunnan of China, is described and illustrated in this study. It possesses extremely large bracts and is closely related to C. tsaiana Hu and C. tschonoskii Maxim., based on the characters of large bract size and bracts without lobes at the base of inner margins. Furthermore, morphological comparison suggested it was distinctly different from C. tschonoskii by a series of characters from leaf, infructescence, bract and nutlet and from C. tsaiana by its leaf length to width ratio (1.4-2.0 vs. 2.0-2.4), lateral veins significantly impressed adaxially, number of lateral veins on each side of midvein (9-14 vs. 14-17), bract length (3.9-4.8 vs. 2.5-3.2 cm) and bract length to width ratio (2.3-3.1 vs. 1.5-2.1). Therefore, this hornbeam, based on only one population from southeast Yunnan, is here erected as a new species, named as C. gigabracteatus.