(15) 土沉香 (牙香樹、白香木)
Aquilaria sinensis (Lour.) Gilg.
瑞香科 (Thymelaeaceae)

英文名 (English name): Incense Tree

中國境內現狀:近危 (NT)。國家二級保護野生植物。已載入《中國植物紅皮書》和《廣東省珍稀瀕危植物圖譜》。
Status in China: Near Threatened (NT). Wild plant under State protection (category II). Recorded in China Plant Red Data Book and Illustration of Rare & endangered plant in Guangdong Province.

形態特徵:常綠喬木;幼枝疏被柔毛。葉互生,革質,倒卵形至橢圓形,長5-11厘米,寬2-4厘米,全緣。花黃綠色,芳香,排成頂生或腋生的傘形花序;花萼5裂,兩面均有短柔毛;花瓣10,鱗片狀;雄蕊10;子房2室,被短柔毛。蒴果木質,倒卵形,長2.5-3厘米,直徑約2厘米。
  

地理分布:香港各地。海南、廣東、廣西、雲南各地。
  

生境與生態:生於低地常綠闊葉林及風水林中。花期:4月;果期:7月。
  

本種是中國特有的珍貴藥用植物,樹幹受真菌侵入後產生的樹脂為中藥“土沉香”,供香料及藥用。葉濃綠,樹冠緊密,可用作庭園樹。潛在的威脅因素包括生境破壞及非法採伐,但本種在香港常見,很多生長地點在郊野公園內,也未受任何特別威脅。香港及華南地區已開始人工繁殖,用作綠化樹種。
    
Description: Evergreen trees, branchlets sparsely pubescent when young. Leaves alternate, leathery, obovate to elliptic, 5-11 cm long and 2-4 cm wide, apex short acuminate, base broadly cuneate, margin entire, glabrous. Flowers yellowish green, fragrant, in a terminal or axillary umbel. Calyx ca. 6 mm, 5-toothed, pubescent on both sides. Petals 10, squamose; stamens 10 in one whorl. Ovary 2-celled, pubescent. Capsule woody, obovoid, 2.5-3 long, ca. 2 cm in diam.
  

Distribution: Various locations in Hong Kong. Hainan, Guangdong, Guangxi and S Yunnan.
  

Habitat and Ecology: In lowland broad-leaved evergreen forest and in fung shui woods. Flowering: Apr.; fruiting: Jul.

This precious medicinal plant is a source of fragrant wood, formed under pathological conditions, called “Chen Xiang”. It is used medicinally and the plant is also used as an ornamental. Potential threats include destruction of habitats and over-exploitation, but the species is common in Hong Kong and currently not under any particular threat. Many localities of its occurrence fall inside Country Parks under protection. The plant has also been artificially propagated in Hong Kong and other cities of southern China.

參考文獻(References)
傅立國,1992: 中國植物紅皮書 1:670-671。科學出版社,北京。
李振宇,1999: 中國植物誌52(1):290。科學出版社,北京。