REVIEWS 993 



In general it may be said that the root systems of a species are often 

 as marked and distinctive as are the above-ground vegetative charac- 

 teristics. The root systems of different species, even of the same genus, 

 may be of entirely different types. The writer concludes that a knowl- 

 edge of position and competition of roots is indispensiblc in explaining 

 the phenomena of succession. It greatly increases the usefulness of 

 plants as indicators of agricultural and non-agricultural land. It helps 

 in solving the problems of competition of range species and the im- 

 provement of the range. If the root systems indicate the distribution of 

 soil moisture in various habitats their study should be of material aid to 

 the forester in selecting sites for reforestation or afforestation. 



It is hoped that this admirable work by Weaver will stimulate other 

 botanists and foresters to undertake research in this fruitful field. 



J. W. T. 



Some Information About Chinese Wood Oil. By D. Y. Lin. M.F., 

 University of Nanking. The Far Eastern Revieiv, Sept., 1919. 



Wood oil or tung oil ranks third in importance of the vegetable oils 

 produced in China, the first two being soya bean and peanut oils. It is 

 used chiefly in the paint and varnish industry, being particularly in de- 

 mand in the United States. Almost the entire output is from the 

 provinces of Szechuan, Kweichow, Hunan, and Hupeh, besides the 

 Kvvangsi product. During the five years 1934-1918, the total export 

 abroad and to native ports amounted to 3,572,397 piculs, or 238,154 

 tons. Of this amount, 2,154.597 piculs, or 143,640 tons, were exported 

 abroad. The annual exports have fluctuated considerably in quantity, 

 showing on the whole a decrease, due largely to political disturbances. 

 On the other hand, the value has increased. Thus the foreign exports 

 for the years 1915-19 J 8 were worth (in round numbers) $1,868,000, 

 $4,254,000, $4,981,000, and $7,530,000, respectively. 



This oil is obtained from the seeds of two species of Alenrites, 

 Tiamely. A. montana and A. fordii, the latter supplying about 90 per 

 cent of the total. The trees grow on poor, rocky soils, withstand 

 drought and heat, and are hardy as far north as 24° or even farther, 

 though they often fail to fruit in the colder regions. The trees grow 

 rapidly, but are mostly rather bushy, with a height usually not over 

 20 feet and a diameter of 6 to 10 inches. 



Plantations are mostly on hillsides, the spacing between about 11 feet 

 each way. They are started either by direct seeding or, less commonly, 



