Tên Khoa học: Luzula effusa Tên tiếng Anh: Tên tiếng Việt: HếnTên khác:
Luzula effusa is a member of sect. Diprophyllatae Satake in T. Nakai & M. Honda (1938: 25), a polyphyletic group of 12, mostly subarctic, boreal, and alpine species (Kirschner 2002, Drâbkovâ & Vlcek 2010). Despite the artificial nature of this section, it can be distinguished from other Luzula infrageneric taxa by the combination of a perennial habit and a much-branched inflorescence with the flowers borne singly within the inflorescence. Luzula effusa is the only species in sect. Diprophyllatae with storied panicles (i.e., inflorescence subdivided into smaller panicles) that are > 1/3 the height of the plant. Our specimen is immature so other diagnostic features, such as anther length shorter than filaments (Wu & Clements 2000) and papillate capsules (Kirschner 2002), are difficult to evaluate. Although Luzula effusa s.l. is considered a highly variable taxon (Kirschner 2002), current treatments recognize two varieties: var. effusa and var. chinensis. Cauline leaves up to 12 mm wide and reddish brown tepals identify our specimen as var. chinensis, although stem diameter is less than 2 mm, which is more characteristic of var. effusa. Although this discrepancy in diagnostic characters could be explained by the immaturity of our specimen, intermediates between the two varieties are known, as are robust forms of var. chinensis, indicating that this polymorphic taxon is in need of further taxonomic study (Kirschner 2002). The identification of our specimen as var. chinensis was based upon our interpretation of the prevailing trend in diagnostic morphological characters.
Luzula effusa s.l. has one of the largest distribution ranges known in Luzula (cf. Kirschner 2002). It is found throughout Eastern Asia with populations recorded from Nepal, Bhutan, China, Taiwan, Malaysia, Borneo, Sulawesi, New Guinea, and the Philippines (Kirschner 2002). Its occurrence in the northern Vietnamese Province of Lao Cai is approximately 500 km southeast of the nearest populations in Yunnan (see distribution maps 45 and 46 in Kirschner 2002), a Chinese province that shares a common border and forest flora with Mount Fansipan and the Hoang Lien Son Range (Nguyen 1998, Sterling et al. 2006).
Luzula effusa was found at 2900 m in a bamboo dominated habitat along a heavily used hiking trail that leads to the summit of Mount Fansipan (3143 m). The fact that L. effusa was only encountered at elevations above 2900 m suggests that this species is restricted to the uppermost reaches of Mount Fansipan. Since very little high elevation habitat, above 2900 m, is found in Vietnam, L. effusa is probably highly localized and likely of conservation concern in this country