980 EXPERIMENT STATION RECORD. 



water-bearing strata, and finally the use of water by growing piants. Because of the 

 smaller amount of evaporation and the greater absorption of the soil, the storage of 

 ground water in considerably greater in the winter than in the summer. The influ- 

 ence of forests on ground water can not be measured where the water-bearing strata 

 is inclined, thus giving rise to stream flow. 



hi the climatic zone of Bavaria, where these experiments were carried on, forests 

 had no effect either on raising or lowering the ground water. It is desired that this 

 conclusion be considered local and as applying to more or less permeable soils. A 

 brief review of other similar work is included. 



Rubber, gutta-percha, and balata, F. Clouth {London: Maclaren & Sons; New 

 York: D. Van Nostrand Co., 1903, pp. XIl+242,figs. 30, maps 2, dgm. 1).— This is the 

 English translation of this work, which first appeared in German in 1899. It contains 

 chapters on the natural history, production, and commercial points of rubber, gutta- 

 percha, and balata, and on their chemical and physical properties. In the case of 

 rubber, there are chapters also on the production of soft rubber goods, vulcanization, 

 hard rubber, and regenerated and artificial rubber. The production and employ- 

 ment of gutta-percha goods is also considered, as well as the principal products made 

 of India rubber, gutta-percha, and balata. 



Rubber tapping- on Kepitigalla estate, I. Etherington (India Rubber World, 

 33 (1906), No. 4, pp. 107-112, figs. 7) . — This estate is considered a typical example of 

 a well- worked plantation of cacao and Hevea brasiliensis. The methods of tapping in 

 vogue are explained, and descriptions given of the coagulating factory and machines 

 for coagulating the latex. The spiral method of tapping is described in detail and 

 illustrated. 



By this method of tapping the average yiela per tree for the preceding year was 

 little over five pounds of rubber. There is very little scrap with this system, and 

 the rubber turned out is of very high grade. It is believed that this system will be. 

 widely taken up on plantations, as it is considered one of the most important forward 

 steps made in the industry for considerable time. 



A new tapping- method for Kickxia elastica, Strunk ( Tropenpflanzer, 10 (1906), 

 No. 3, pp. 141-149, figs. 6). — In place of the herring-bone method of tapping, the 

 author uses simply perpendicular slits placed about 10 cm. apart. 



The yield of rubber obtained is claimed to be fully as great and the trees are much 

 less injured. The yield of rubber is increased if the slits are made at intervals of 

 about 4 weeks. The old slits are not reopened until after several years, when they 

 are completely healed. It is believed that by this method of tapping the work can 

 be much more rapidly performed and the profits considerably incieased. Illustra- 

 tions are given showing the methods of tapping followed and the tools used for 

 making the cuts. 



Report on the experimental tapping- of Para rubber trees in the botanic 

 g-ardens, Singapore, for the year 1904, H. N. Ridley and R. Derry (Agr. Bui. 

 Straits and Fed. Malay States, 4 (1905), No. 11, pp. 424-443, pis. 2).— Experiments 

 have been carried on with 84 groups including 880 Para rubber trees during the past 

 year. These trees produced a total of 884.5 lbs. of dry rubber. 



Various methods of tapping have been investigated. The single incision method 

 is quickly performed, but gives only about one-half the product obtained by the 

 herring-bone method. Trees tapped with the single incision do not recover well and 

 the bark is made difficult for any other method of tapping. It is noted that trees 

 tapped late or early in the year are the slowest to recover. Para rubber trees appar- 

 ently make their most rapid growth between the sixth and fifteenth years of life, 

 making an annual increment of growth in the trees under observation of 3 to 6 in. 



Closely planted trees do not make satisfactory increment of growth, and the yield 

 of rubber increases with the size of the tree from under 0.25 oz. of dry rubber to the 

 inch of girth for small trees to over 0.5 oz. for large ones. This point is further 



