19191 DEBEA8ES OF PLANTS. 843 



gray birch is dependent upon the density of the birch, and la regulated more 

 by the competition for soil moisture and nutrients than by the shade of the 

 birch canopy. Pure stands of gray birch of all densities may be onderplanted 

 wit li white pine and the birch removed when the slowing down of growth in 

 the pine or the economic utilisation Of the bhvh makes it advisable. 



The regeneration of sal (Shorea robusta) forests. K. S. Hots (Indian I 'or- 

 Otter, !,5 (1919), No. 8, pp. 119-132, fly. 1). — A summary of conclusions, based on 

 the results of a long series of experiments carried out at Dehra I>un in re- 

 c'ii! years, Including a sketch of the proposed system of regeneration. 



Mahogany and some of its substitutes, S. J. RECORD {.lour. I r, 11 



(1919), No. 1, pp. 1-8). — A contribution from Yale School of Forestry, Com- 

 prising a descriptive key based on the gross and lens characters of most of 

 the woods known to the trade as "mahogany," or used as a substitute for the 

 true mahogany. 



Tapping experiments on Hevea brasiliensis, A. W. K. Dl JoHfl < Irch. Rub- 

 berou.lt. Nedcrland. Indii', 8 (1919), No. 1, pp. 1-6). — Results are given of tap- 

 ping experiments conducted over a period of f>A years. 



Preliminary note on the seasoning of some Indian timbers, by natural 

 methods, R. S. Pearson (Indian Forest Rec, 7 (1918), No. 1, pp. 1.',. pi. />. — 

 Preliminary data are given on seasoning tests conducted with some :<•". Bpedes 

 of Indian timbers. 



A formula method for estimating timber, E. I. Terry (Jour. Forestry, 17 

 (1919), No. 4, pp. J f 13-J f 22, fig. 1). — With tree measurements made by the author 

 and others in the western yellow pine region of Colorado as a basis, the author 

 evolved a board-foot form factor method which is here presented as a means 

 of Simplifying the work of computation in working out timber estimates. The 

 application of the method is described. 



Appraisal of fire damage to immature timber for statistical purposes, I" < '.. 

 Clark [Jour. Forestry, 17 (1919), No. 1, pp. 56-38).— The author here prop, 

 a modified replacement formula, which it is believed will overcome certain 

 difficulties met with in the use of straight expectation or replacement methods 

 of appraising tire damage to immature timber. 



Production of lumber, lath, and shingles in 1917, F. 11. Smith and A H. 

 Pierson (U. S. Dept. Agr. Bui. 768 (1919), pp. -',.',. figs. 5).— Detailed statistics 

 are given of the 1917 production of lumber, lath, and shingles, with comparative 

 figures from previous annual reports (E. S. R., 39, p. 45'J). The production Is 

 given both by States and by species. 



The estimated total lumber production in 1917 was 30,000,000,000 ft. b. in., or 

 a decrease of 10 per cent over the estimate for 1916. 



DISEASES OF PLANTS. 



A convenient heating and sterilizing outfit for a field laboratory. G. L. 

 Peltier and D. C. Neal (Phytopathology, 8 (1918), No. 8, pp. #6-438, figs. >>.— 

 The authors report having found an autoclave used in home canning work well 

 suited for use for heating and sterilizing in field laborator 



Imbedding and staining of diseased wood, J. S. Boyce (Phytopathology, 8 

 (191S), No. 8, pp. 432-J,S6).— The author describes some modified practices 

 which have been found very satisfactory for the study of Ugnlfled tissues in- 

 vaded by fungus mycelium. 



Preparation of copper and copper-arsenic sprays, Liautard (Prog. Agr. it 

 Vit. (Ed. VEst-Centre), 89 (1918), No. 85. pp. 585-590, figs. 2).— The author gi 

 an account of means and methods employed in successful operations against 

 animal pests and grape mildew in Boufarik, Algeria. 



