THE MORE IMPORTANT PLANT PRODUCTS 73 



certain purposes Chinese nut-galls furnish the finest tanning 

 material in the world. These "nut-galls" (" Wu-pei-tzu ") 

 develop on the leaves of Rhus javanica, "Peh-fu-yang shu," as 

 an excrescent growth due to protoplasmic irritation, occasioned 

 by an insect [Chermes) which punctures the leaf to deposit its 

 eggs. The tree is of small size, and very abundant in the 

 Yangtsze Valley up to 3500 feet, more especially in rocky 

 places, producing panicles of white flowers in late August and 

 September. The galls are hollow and brittle, and vary con- 

 siderably in shape and size, being more or less irregular, and i to 

 4 inches long. In China they are used for dyeing blue silk and 

 blue cotton cloth black. The Occidental demand for nut-galls 

 is greater than the supply, and the exports increase annually. 

 In 1900, 24,800 piculs, valued at Tls. 454,584, were exported 

 from Hankow ; in 1910 the exports from this port had in- 

 creased to 53,784 piculs, valued at Tls. 936,234. 



Another less common species is R. Potaninii, colloquially 

 known as the " Ch'ing-fu-yang," which produces galls known 

 as " Ch'i-pei-tzu." These are used in Chinese medicine. 

 The world is sadly in need of an indelible black ink, and 

 chemists might weU turn their attention to Chinese nut-galls in 

 their quest for this treasure, since they possess possibilities 

 worthy of investigation. 



In the chapter on fruits reference is made to the cultivated 

 Persimmon {Diospyros kaki), but it is necessary here to 

 mention the feral form, known as " Yu-shih-tzu " (literally 

 " Oil Persimmon "). This wildling is abundant in the moun- 

 tains of central and Western China up to 4000 feet altitude, 

 where it forms a large tree 50 or 60 feet tall. The fruit varies 

 from flattened-round to ovoid, and from f to 2^ inches in dia- 

 meter. It is always rich golden yellow in colour when ripe, 

 and this colour best distinguishes the smallest fruited forms 

 from its close ally Diospyros Lotus, " Kou-shih-tzu," which has 

 flattened-round fruit, dark purplish coloured when dead ripe. 

 To obtain the varnish oil for which this tree is esteemed, the 

 fruit is plucked in July when about the size of a crab-apple, 

 and still green. By means of a wooden mallet the fruits are 

 reduced to pulp, which is placed with cold water in large 

 earthenware jars fitted with covers, and allowed to decompose. 



