A Study of the Genus Hemiboea (Gesneriaceae) (Cont.)
半蒴苣苔属的研究(续)

The genus Hemiboea is a curious genus of the tribe Didymocarpeae (Cyrtandroi- deae), characterized by its peculiar pistil with one fertile carpel and its follicle-like capsule. This genus has not yet been thoroughly studied since its establishment by C. B. Clarke in 1888. In the present paper, the taxonomic history is briefly reviewed; the external morphology, leaf his- tology, pollen morphology and geographical distribution are discussed; a key to the 21 species recognized by the author is provided; and the economic uses reported in various publications are summarized. I. Morphology (1) Sclereids The foliar sclereids, occurring in this genus and defined by their forms, fall into two types. (A) Vermiform selereids This type of sclereids is noted in 15 species and may be clas- sified into two groups according to their positions in leaf tissues. Those of the first group are interspersed in the ground tissue around the vascular bundles of leaves and noted in 12 species, i.e.H. longisepala, H. cavaleriei, H. bicornuta, H. fangii, H. omeiensis, H. gracilis, H. glandulosa, H. mollifolia, H. pingbianensis, H. parviflora, H. strigosa and H. gamosepala, and those of the second group are dispersed in the mesophyll, occurring in H. subcapitata, H. henryi and H. latisepala. (B) Astrosclereids The sclereids of this type are discovered for the first time in Hemiboea, dispersed in the mesophyll of a single species, i.e.H. lungzhouensis. No foliar sclereids are found in the remaining 5 species, i.e.H. integra, H. flaccida, H. longgangensis, H. subacaulis and H. follicularis. The differences in forms and positions of the foliar sclereids and their absence or pre- sence are of great help in understanding the relationship between the infrageneric taxa. (2) Pollen grains The pollen grains of 19 species were examined with LM and SEM. They are 3-colporate, subglobose or prolate, 20-38.8×22-28μm. The exine is 1.3-2μm thick and the sculpture is foveolate (e.g.H. cavaleriei) to reticulate (e.g.H. omeiensis). In Sect. Subcapitatae the pollen grains are subglobose or prolate, while those of Sect. Hemiboea are prolate. No pollen grains are observed in anthers of 13 speciemens of H. subacaulis var. subacaulis and var. jiangxiensis. (3) Seed-coat Under SEM the seed-coat exhibits considerable diversity in the genus, fur- nishing useful characters for explaining the relationship between the two sections. 2. Geographical distribution The genus Hemiboea ranges from the eastern border of the Xizang Plateau and Yunnan Plateau eastwards to Ryu Kyu Islands, and from the southern slope of the Qinling Range southwards to northern Vietnam. The karst region of S. E. Yun- nan and W. Guangxi is the centre of maximum variation of the genus and is probably its origin centre, where the most primitive taxon exists, and where more species (13 species, i.e. 61.9 per cent of the sum total) and more endemic species (8 species)