80 NOTES ON THE AGRICULTURE, BOTANY 



sively grown in the country ; the most common of them is the 

 Mongolian oak (Quercus mongolica). The bark contains 

 about 6-11% of tannin. 



3. — Willow. (Salix Caprea L., 8. viminalis L., 8. 

 vagans Anderss., 8. triandra L., S. Thunbergiana Blume, 

 S. purpurea L., 8. pentandra L. and 8. acutifolia Willd.) of 

 Salix Caprea L. and 8. acutifolia Willd. are the most useful 

 for tanning. The bark of the willow contains about 11% of 

 tannin. 



4. — Amurian acacia (Cladrastis amurensis Benth.) It 



is a small tree or shrub very common in all districts. The 



■ chemical analysis made in Harbin by Mr. Karwowskii in 1918 



shows that the bark of this acacia contains 11% of tannin. 



For this reason this plant is worthy of attention. 



5. — Ajanien fir (Picea ajanensis Fisch.). It grows in 

 mountainous districts and its bark can be used in tanning. 

 Picea bark has 8-11% of tannin. 



With regard to the other tanning plants, growing wild in 

 Manchuria, not one is of sufficient importance to occasion 

 remark. 



XX. — On the Cultivation of Water Plants in China. 



Indubitably, on the surface of small ponds and in dirty 

 stagnant basins many persons have seen a mass of very 

 small, mostly round green leaves with roots under the water. 

 These plants are used to feed fowls in China. In Manchuria 

 and in North China they are represented by the small duck- 

 weed Lemna minor L., L. trisulca L., Spirodela polyrrhiza 

 8chleid; in middle and south part, except the indicated 

 forms, by Wollfia arrhiza Wimm., 8alvinia natans L., Azolla 

 sp., Marsilia guardrifolia L. and other kinds. All these 

 plants show the dirtiness of the waters and are very often 

 seen near Chinese buildings, villages and towns in summer 

 and in winter time. In Manchuria a great quantity of Lemna 

 minor L. and L. trisulca L. is met with in marshes and ravines 

 lying near the houses and are mostly used in towns by poor 

 Chinese as food for ducks and geese. In Middle and South 

 China these plants are not only gathered in rice fields and in 

 ravines near the roads to feed fowls, but are also cultivated 

 in ponds. For this reason the surface of the ponds is divided 

 in parts by thick and long floating bamboo poles, that con- 

 tribute to the growth of these small water plants. Without 

 these, owing to the movement of the surface of the water, 

 these small water plants would not grow. Mostly as food for 

 • ducks the duckweed Lemna minor and the 8pirodela poly- 

 rrhiza is used and cultivated. The latter in South China has 

 the leaves twice bigger than that in Manchuria. At Foochow 



