46 EXPERIMENT STATION RECORD. [Vol. 40 



of results of stand measurements of several Indian tree species that have 

 been made for varying periods of years either in divisional sample plats or in 

 Forest Research Institute sample plats. The data presented for each species 

 deal with one or more of the following measurements: Girth, volume, and height 

 increments ; yield, stem analysis, and comparative growth of natural and 

 plantation saplings ; and effect of thinnings. 



Some forest species of Indo-China suitable for national defense, A. Bert- 

 band (Bui. Eeon. Indoehine, n. ser., 21 (1918), Xo. ISO, pp. 438-446).— This com- 

 prises an extract from the author's report to the Colonial Congress of Agricul- 

 ture at Paris. Information is given relative to the mechanical properties of 

 a number of Indo-China woods, including data on mechanical tests conducted 

 with these woods. 



Field experimentation with Hevea brasiliensis, J. Grantham and M. D. 

 Knapp (Arch. Rubbercult. Ncdcrland. Indie, 2 (1918). Xo. 8, pp. 614-636, figs. 

 3). — The authors present additional data substantiating evidence previously 

 reported that natural variations may occur among carefully chosen experimental 

 plats (E. S. R., 37, p. S37). The value of applying the probable error method 

 to field experimentation is emphasized by showing the application of the rule 

 that "the weights (or relative reliability) of observations (or results) vary 

 inversely as the squares of their probable errors." Additional data recording 

 the probable error of rubber yield are given from which is ascertained the 

 probable error that should be used in field experimentation with Hevea for 

 plats of varying sizes. 



Reliability of field experiments with Hevea, J. 6. J. A. Maas {Arch. Rub- 

 bercult. \, dryland. Indie, 2 (1918), Xo. 8, pp. 561-613, ph. 4. figs. 5).— The ob- 

 ject of the investigations here reported was to collect figures on the natural 

 variation in the yield of rubber fields under estate conditions to show the limits 

 up to which differences in yield in field experiments may be due to natural 

 variation and how such limits can be altered by alterations in the experiments. 



As a result of this study it is concluded that in order to fix the relation be- 

 tween the yield of the experimental plats a preliminary experiment of three 

 months is sufficient for practical purposes. In a well-planned experiment the 

 standard deviation for this period need not exceed 5 per cent. The plats should 

 not be smaller than 100 trees. 



The budding of Hevea, W. M. Van Hki.ten (Teysmannia. ':• [1918), Xo. 5. 

 pp. 216-284, pi. 1). — Comparative results are given of experiments in which 

 three different forms of shield budding were used for propagating Hevea 

 rubber trees. 



Guide to the preparation of rubber. P. Arens (ifalang, Java: K.rjit. Sta. 

 Malang, 1918, pp. 50; trans, from Medcd. Proefstat. ilalang. Xo. 11 (1917), pp. 

 61). — A practical guide to the plantation preparation of various types of rub- 

 ber, with special reference to the acetic-acid process, translated from the sec- 

 ond Dutch edition. 



Rubber: Its production, chemistry, and synthesis, A. Di and A. I.tt- 



tringer (London: Charles Griffin d Co., Ltd., J'JlS, pp. XI+3S3 ; rev. in Cheni. 

 News, 111 (1918), Xo. 3059, p. 338).— This is an English translation by E. YV. 

 Lewis of a practical handbook for the use of rubber growers, chemists, and 

 economists. The subject is discussed under the following general headings: 

 Natural rubber, its production, present position, and cost of production; the 

 formation, physical and mechanical properties, analysis, and constitution of 

 crude rubber; and the synthesis of caoutchouc. 



Note on the mangrove forests of British India, R, S. Pearson (Trans. 3. 

 Internal Cong. Trop. Ayr. 191',. vol. 2. pp. 625-633).— A short account of the 



