The rare and threatened plants in Fujian Province were investigated in winter of 2014. We started from the core of Zhonghuang in the Tingjiangyuan National Nature Reserve in the beginning of December, climbed over the Wuyi Mountain Watershed and then entered into Ganjiang River basin from Tingjiang River basin, a sippet evergreen broad-leaved forest was found in a valley of the Gucheng Town, named Magezhai (25°48′30″ N, 116°10′53″ E). The upper layer is composed of tall tree species, such as Castanopsis tibetana, C. fordii, C. lamontii, C. fargesii, Altingia gracilipes and Phoebe bournei. The middle layer is consist of Machilus pauhoi, Acer pubinerve, Mallotus lianus, Engelhardia fenzelii, Vernicia montana and Huodendron biaristatum var. parviflorum. The lower layer is dominant by an unknown bamboo with the local name Cheng Huang Zhu (城隍竹).

Based on several field investigations and observation by artificial cultivation during recent two years, this species rhizomes are amphipodial (Fig. 1: C), showing that it isn't attributed to the genus Indosasa McClure and Acidosasa C. D. Chu et C. S. Chao^[1-3], because the rhizomes of Acidosasa and Indosasa are monopodial. Secondly, the two ridge villus of prophyll outside the bud of the young stem is light gray (Fig. 1: E), which means the species doesn't belong to Sinobambusa Makino ex Nakai^[1-2], because Sinobambusa was purple hairs. Finally, culm internodes of this species are strongly flattened above branches; culm supra-nodal ridge substantially raised (Fig. 1: F), which coincides with the discriminant feature of the genus Oligostachyum listed in the key of Flora of China^[4].

In addition, the culm sheaths are purple-green when fresh, pale brown when dry; absence of auricle and oral setae, or with only 1-2 setae on the lower culm sheath; leaves usually 2-3 per ultimate branch, are linear-lanceolate with a width of no longer than 1.5 cm etc. Overall, we strongly believe that this species is a new member of the genus Oligostachyum.

The genus Oligostachyum Z. P. Wang & G. H. Ye includes 16 species and all distributed in China^[4]. From the Wuyi Mountains and its east, to the five ridges mountains, some species up to the middle of the Yangtze River Basin. There are 7 species recorded in Fujian^[1]. A key to the known species of Oligostachyum from Fujian is provided below.

Key to Oligostachyum species from Fujian

1a. Culm internodes obclavate, lower ones gradually thickened downward; midculm branches 3–7 per node, subequal in diam. …………………………………………………………………………………………………… O. oedogonatum 肿节少穗竹

1b. Culm internodes of culm cylindrical, not thickened, midculm branches 3 per node, or if more than 3, then conspicuously unequal in diam.

2a. Culm sheath abaxially strewn with brown strigose hairs or later with striae; culm sheath ligule long brown ciliate ………………………………………………………………………………………………………………………… O. spongiosum 斗竹

2b. Culm sheath abaxially sparsely setulose; culm sheath ligule glabrous or short ciliolate.

3a. Culm sheaths densely retrorsely setulose at base; culm internodes and leaves abaxially puberulent …… O. heterophyllum 城隍竹

3b. Culm sheaths without setulose at base; culm internodes and leaves abaxially mostly glaucous.

4a. Culm sheaths dark brown or straw-colored when dry; leaf sheath ligule the length is 3 mm …… O. exauriculatum 无耳少穗竹

4b. Culm sheaths uniformly straw-colored when dry; leaf sheath ligule less than 2 mm.

5a. Basal culm sheaths with longitudinal spots or streaks ……………………………………………… O. scabrifolium 糙花少穗竹

5b. Basal culm sheaths without longitudinal spots or streaks.

6a. Culm sheaths pubescent at base only ……………………………………………………………… O. glabrescens 屏南少穗竹

6b. Culm sheaths uniformly setose or strigose.

7a. Culm sheaths without auricles and oral setae, uniformly thickly white powdery …………………………… O. sulcatum 少穗竹

7b. Culm sheaths with small auricles and developed oral setae, without powder ……………………………… O. lubricum 四季竹

Oligostachyum heterophyllum M. M. Lin sp. nov.  城隍竹 Fig. 1

Rhizomes amphipodial. Culms erect, slightly zigzag, 3-4 m tall, 1-1.5 cm in diam.; pith spongy; internodes 15-35 cm, pale gray-green, initially pubescent, flattened with longitudinal ridges and grooves in the branching side, white powdery especially below nodes; culm nodal ridge significantly prominent, sheath scar initially with short and brown setae. Intranodes 5 mm wide, smooth. Branched 3 at each node, middle branch thicker and longer. Culm buds ovate, adnate, margins peritrichous. Culm sheaths caducous, purple-green when fresh, pale brown when dry, thinly leathery, 1/2-2/3 as long as internodes, ovate-triangular, abaxially clavate-setose, lengthwise veins distinct, cross-connecting veinlets indistinct, densely setulose at base, margins ciliate; auricle absent, oral setae absent on sheath margins or sometimes 1-2 erect oral setae in 1-2 mm length; ligule truncate or slightly prominent, pale stramineous, ca. 1 mm tall, margins short ciliolate; blade lanceolate, 1-2 cm long, 2-3 mm wide, abaxially pubescent, margins sparse ciliate. Leaves dimorphic, 4-5 on the branchlets at the apex of the culm, larger, 15-25 cm long, 3-4.5 cm wide, secondary veins 6-8 pairs; others (1)2-3(5) per ultimate lateral branch, smaller, leaf sheath pale green, pubescent, upper margins ciliate; auricle absent or sometimes 1, oral setae absent on sheath margins or sometimes 1(3) in 2 mm length, erect; ligule developed, ca. 3 mm prominent, pale grey, pubescent; petiole 2-3 mm long, abaxially pubescent; blade lanceolate or narrowly lanceolate, 8-15 cm long, (0.6)1-1.5(2) cm wide, thick papery, apex lanceolate and finely acuminate, base cuneate to rounded-cuneate, adaxially glabrous, abaxially greygreen, pubescent, secondary veins 4-5 paired, crossconnecting veinlets sightly distinct, margins serrated and scabrous. Inflorescence unknown. New shoots in March.

Fujian: Changting County, Gucheng Town, Magezhai, 25°48′30″ N, 116°10′53″ E; alt. 500 m, near a stream in a valley, understory; 2015-04-24, LIN Qin-wen et al. 01-06 (holotype, FJFC).

This species is close related to O. scabriflorum. But this species differs from O. scabriflorum by smaller culm with a diameter less than 1.5 cm, culm sheath palely purplish-green clavate-setose and not spotted abaxially, no white powdery and scorched edge, base with densely fine setae, ligule pale stramineous, blade erect, base unshrinked, leaf sheaths puberulous.

Acknowledgment: We thank Prof. Sha-sha WU (College of Landscape Architecture, Beijing Forestry University) for his guidance in English.