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Based on herbarium and field observations, a new species, Holcoglossum nujiangense, is described and illustrated. It is morphologically similar to Holcoglossum sinicum and H. weixiense. Holcoglossum nujiangense differs from H. weixiense by smaller flowers with broadly rhombic midlobe and from H. sinicum by its broadly rhombic midlobe, papillose spur and notable callus on the disc. The chromosome number of this species was found to be 2n = 38. The pollinator for this new species was Micraphis andreniformis Smith that carried the pollinia of Holcoglossum nujiangense on its head. The visiting behavior of the pollinator is food-search kind, although there is no obvious nectar in the spur.

The flower structure and development of ten species in six genera of the orchid subtribe Orchidinae are described and illustrated by scanning electron micrographs. Particular attention is given to the structure of the gynostemium, which for most species is interpreted from ontogenetic data. All the species studied here share a series of features, e.g. the sequence of tepal and anther initiation, the shape and position of the anther, the presence of auricles and basal bulges, the three-lobed condition of the median carpel apex and the lateral lobes of the median carpel embracing the basal ends of the thecae. However, the form and structure of the three carpel apices are most varied in the later development stages or in the adult flower. The genus Hemipilia shows a series of peculiar characters that are quite different from those of the other genera in Orchidinae. The peculiar structure and development of the viscidia in both Amitostigma and Neottianthe indicate that both of them are different from other genera in Orchidinae. The adult floral morphology shows that the genera Galearis and Chusua are not congeneric with Orchis. The separation of the lateral lobes of the rostellum in most genera studied here as well as in the Brachycorythis group from South Africa suggests that this is the ancestral state in the subtribe Orchidinae. In contrast, the conjoining of lateral lobes in Dactylorhiza and Orchis is suggested as a derived character.

Interactions between Hemipilia flabellata and anthophilous insects were studied in northwestern Yunnan, China during June‐July of 1996 and 1997. Twenty-seven species of insects were seen visiting the flowers of this species, although only male and female individuals of the bee Anthophora mangkamensis Wu were observed carrying the pollinaria. The frequency of visits by A. mangkamensis to this orchid was rather low. Pollinating bees normally sampled only the lowermost flowers in an inflorescence, staying for 1‐3 seconds. This species is also characterized by low pollination, low fruit set (1‐22%) and a very striking decrease in fruit production from bottom to top of the inflorescence. All of these indicate that the orchid may rely on deception to attract visitors. Ajuga forrestii Diels (Labiatae) appears to be the main or exclusive subsidiary nectar source for A. mangkamensis during the flowering period of H. flabellata. It appears that H. flabellata utilizes a food deceit pollination strategy for pollination. The orchid benefits from the great variation of flowers in colour and shape. Phenological, functional-morphometric and distribution data indicate that A. mangkamensis is an optimal pollinator of H. flabellata and thus the anthecological adaptation of the orchid to the pollen vector may be unique.

BACKGROUND: Holcoglossum is a small orchid genus of 12 species ranging from SW China to Thailand and NE India. Although molecular and morphological analyses have been performed to establish the phylogenetic relationships within this genus, the interspecific relations and its relations with allied genera, such as Rhynchostylis, Aerides and Vanda, remain unclear. METHODOLOGY/PRINCIPAL FINDINGS: In addition to morphological analysis, maximum parsimony, maximum likelihood, and Bayesian inference analyses were performed based on fragments of the nuclear ITS and chloroplast trnL-F and matK genes of 31 taxa (15 Holcoglossum, 14 Aeridinae, 2 outgroups) representing all major clades of the Holcoglossum alliance. The results suggest that Holcoglossum is triphyletic, comprising three clades: the Holcoglossum clade, its sister clade, and a distant clade more closely related to Rhynchostylis, Aerides, and Vanda than to the Holcoglossum clade. The Holcoglossum clade is further divided into three subclades; the genetic distances between these three subclades also support this delimitation. The molecular conclusion is consistent with their distinct morphological characters. CONCLUSIONS: We propose that the latter two clades comprise two new genera, Paraholcoglossum and Tsiorchis, and Holcoglossum clade divides into three sections. In addition, a new section, Holcoglossum sect. Nujiangensia, and a new species, Holcoglossum linearifolium, are proposed. Some new combinations are made, and a new scheme is provided for the classification of all species of Holcoglossum, Paraholcoglossum, and Tsiorchis.

New rank is proposed for Epipactis humilior (Tang & Wang) S. C. Chen & G. Zhu and E. helleborine (L.) Crantz var. tangutica (Schlech- ter) S. C. Chen & G. Zhu. Epipactis humilior was formerly treated as a variety of E. mairei Schlech- ter, but distinctly differs from the latter by having a slender, creeping, elongated rhizome, ovate-lan- ceolate or lanceolate leaves 2-3 cm wide and scarcely or slightly scabrous adaxially. Epipactis helleborine var. tangutica is characterized by pos- sessing on the epichile two much larger fleshy calli rather than small semiorbicular warty lamellae seen in E. helleborine.