6) 齒牙黑桫欏
Gymnosphaera hancockii (Cop.) Ching
桫欏科（Cyatheaceae）

英文名 (English name): Toothed Black Tree-fern

中國境內現狀: 易危 (VU)。 國家二級保護野生植物。
Status in China: Vulnerable (VU). Wild plant under State protection (category II).

Photo credit: Dr. M. L. So

形態特徵：中型蕨類植物，株高60-100厘米，主幹短，常橫臥，密被鱗片。葉簇生；葉柄暗棕色，散生有疣狀突起；葉片披針形，二至三回羽狀深裂；羽片互生，有短柄，長圓形，最大的長達30厘米；小羽片互生，近無柄，長圓形，深裂近達中脈；裂片長圓形，稍偏斜，頂端圓鈍，邊緣具鋸齒，基部1-2個裂片常分離；葉脈羽狀，單一或少有二叉。孢子囊群圓形，著生於側脈中部，沿中脈兩側各排成1行；無囊群蓋。

地理分布：大東山、東涌、大帽山。廣東、江西、福建、台灣；日本。

生境與生態：生於密林下和溝谷或溪邊。

本屬植物曾置於桫欏屬（Alsophila）中，其系統位置尚存在爭議，具有學術研究價值。部分黑桫欏生長在郊野公園內而受到保護。本種受《林務規例》(香港法例第96章附例) 及《動植物(瀕危物種保護)條例》(香港法例第187章)保護。

Description: Medium-sized ferns, 60-100 cm tall. Trunk short, sometimes prostrate, densely covered with scales. Leaves tufted; stipes slender, reddish brown, with scattered warts; lamina lanceolate, bi-to tripinnate; pinnae alternate, short-stipitate, oblong, longest to 30 cm long; pinnules alternate, subsessile, oblong, divided almost to the costa; segments oblong, more or less oblique, apex rounded, margin toothed; one or two basal segments sometimes free; veins pinnate from the costa, simple or rarely forked. Sori rounded, borne on the middle of veins, in one series along each side of the costa, without indusium.

Distribution: Sunset Peak, Tung Chung, Tai Mo Shan. Guangdong, Jiangxi, Fujian, Taiwan; Japan.

Habitat and Ecology: Thick forests of valleys or streamsides.

The species was previously placed in the genus Alsophila. Its systematic position is still controversial and is thus of great botanical interest. In Hong Kong, some localities of its occurrence are protected in Country Parks. This species is also protected by the Forestry Regulations (Cap. 96 sub. leg.) and the Animals and Plants (Protection of Endangered Species) Ordinance (Cap. 187).

參考文獻 (References)：
Edie, H. H., 1977: Ferns of Hong Kong, 87. Hong Kong Univ. Press. Hong Kong.
So, M.L., 1994: Hong Kong Ferns, 44. The Urban Council, Hong Kong.