392 



KNOWLliDGE. 



OCTOUER, 1912. 



leaves, there is n loss of from twenty to forty-five per cent, of 

 the tot.il dry weight in the case of decidiious trees. This 

 remarkable result emphasizes the great expenditure of energy 

 .and material during growth. In the case of coniferous trees, 

 however, there is a much smaller loss, or even a small gain, 

 which may be explained by the fact that these trees .are able 

 to make new food by means of their old leaves, at an early 

 period in spring, and thus make good the loss by respiration 

 during the opening of the buds. It is suggested that in spring 

 the abundance of soil-water and stored food lead to a sort of 

 temporary overfeeding in deciduous trees, and to this they 

 consider the large-celled character of the spring-wood is related. 

 The second outburst of growth which often occurs later in the 

 year, is also caused frequently by abundant supply of water, 

 and in this case also a ring of " spring " wood is produced. 

 In pines growing on rich low-lying moors, the wood is practic- 

 ally all of the same char.acter as the spring wood ; in such a 

 habitat water and food-substances are abundant throughout 

 the growing season. 



From extensive ash analyses it was found that, excepting in 

 the conifers, practically no nitrogen was absorbed during the 

 spring, while the leaves were expanding. The time of 

 maximum absorption of nitrogen varies according to the 

 species, then falls olT in late summer ; in the Alder, owing to 

 the presence of the root-nodules with their nitrogen-fixing 

 bacteria, the absorption of nitrogen continues steadily from 

 May to November. The time of maximum absorption of 

 each of the elements — potassium, calcium, magnesium and 

 phosphorus — varies in diflferent species; while in the same 

 species the various elements are absorbed at different times 

 and at rates which vary independently. For instance, the 

 pine absorbs nitrogen most rapidly in June, calcium in 

 .August. 



/^on and Graves! U.S. Dcpt.,A^ric., Forest Service liullctin 

 No. 92, 19111 have studied the influence of lighten the growth 

 of trees. Their admirable memoir deals with the different 

 kinds of light — direct, diffused, overhead, lateral, reflected. 

 Diffused light is the most important, but some trees need 

 direct as well as diffused light, either during their whole life or 

 at the time of leafing and of flowering. A table is given 

 showing the decrease of direct and diffused light with increase 

 of latitude, direct light decreasing most until at the poles it is 

 zero, whereas diffused light is 20 ; at the equator direct light 

 is 489 as against 227 for diffused light. The authors also 

 discuss the variation of direct and diffused light quantities with 

 altitude, and the minimum light needed for various trees, but 

 the greater part of their paper is devoted to the question of 

 shade-tolerance, or the ability of trees to endure shade, and the 

 way in which this tolerance is influenced by climate.altitude, soil 

 moisture, soil fertility, and the age and vigour of the tree. 

 The methods of determining tolerance are discussed under 

 three he<adings: — (11 empirical methods — observations on 

 density of the crown, amount of branching, and so on ; 

 (2) anatomical and physiological methods — minute structure 

 and assimilation capacity of the leaves ; 13) physical methods 

 — measurement of luminous and chemical light intensities. 



Preston and Phillips [Forestry Quarterly, 1911) have 

 enquired into the nature and variation of the reserve food 

 materi.ils in certain American trees, comparing their results 

 with those obtained by European investigators. Starch seems 

 to be the .chief reserve food, and in temperate climates a 

 great reduction in its amount occurs during the first weeks of 

 winter, though there is no great increase in the amount of 

 sugar except at the unfolding of the buds in Spring. The 

 maximum for reserve starch in deciduous trees appears to be 

 at the period of leaf-fall, while in evergreens it is at the open- 

 ing of the buds in Spring. 



CHEMISTRY. 



By C. AiNsvvoRTH Mitchell, B.A. (Oxon.), F.I.C. 



RED PHOSPHORUS.— The Berichte of the German 

 Chemical Society (1912, XLV, 1514) contains an interesting 

 account of experiments made by Messrs. Stock, Schrader and 

 Staium upon theconditions for converting ordinary phosphorus 

 into the red modification by means of radiation. The influence 



of red rays and ultraviolet rays was verj' slight, the greatest 

 effect being produced by visible rays in the violet part of the 

 spectrum. When exposed to radiations of a mercury-vapour 

 lamp or an induction spark the phosphorus changed through 

 yellow to red and subsequently became opaque, probably owing 

 to the co.agnlation of the colloidal solutions first formed. 



The red phosphorus formed under the influence of radiation 

 ignited at 4 JO — 440° C, ordinary phosphorus probably being 

 produced before ignition. The darker the specimen the 

 greater was its specific gravity, which ranged from 1'95 to 

 2 • 25 ; and considerable differences were also observed in the 

 various preparations as regards the rate with which they 

 would combine with oxygen. Apparently they were all 

 amorphous in structure. 



When ordinary phosphorus vapour was heated to a tem- 

 perature of about 1000° C. and then suddenly cooled it yielded 

 an amorphous red modification, whereas when the cooling 

 was done slowly there was no such change. The explanation 

 suggested is that the high temperature causes dissociation of 

 the Pj molecules, and that the sudden chilling causes the 

 resulting smaller molecules to combine together or with 

 undissociated P, molecules to produce a red modification. 



This phosphorus is red and transparent in thin layers, but 

 appears violet-black in large masses. It has a somewhat 

 lower specific gravity than ordinary red phosphorus, and is 

 also more permanent when e-xposed to the air. It also offers 

 great resistance to the action of boiling sodium hydroxide 

 solution. 



CHEMICAL REACTIONS AT IlICll PRESSURES.— 

 An apparatus has been devised by Dr. F. Bergins iZeit. 

 tnificicait. Clietn., 1912, XX\'., 11711. for studying the process 

 of chemical reactions under pressures maintained at over one 

 liundred and fifty atmospheres for several weeks and at high 

 temperatures (300° to 400°C.). Underthese conditions carbon 

 will react with water at 350'C.. in the presence of a catalytic 

 agent, with the formation of hydrogen and carbon dioxide. 

 Aromatic hydrocarbon hydroxyl derivations, such as naphthol 

 and phenol were obtained in the same way at a pressure of 

 one hundred atmospheres by the interaction of solutions of 

 alkalies upon the corresponding hydrocarbon chlorine deriva- 

 tive ; while oxygen could be made to combine directly with 

 calcium oxid'; to form calcium peroxide. 



But perhaps the most interesting reaction was the pro- 

 duction of an artificial coal of very similar composition to 

 natural coal. This was obtained by heating either peat or 

 cellulose with water to about 340°C. at a high pressure. This 

 method also seems likely to throw light upon the mode of 

 formation of petroleum and its derivatives. 



DISTRIBUTION OF NITROGEN IN WHEAT.— A 

 series of estimations of the distribution of nitrogen in the 

 different parts of the wheat grain has been made by Messrs. 

 Greaves and Stewart (Jotirii. Agric. Science, 1912, IV, 376), 

 the wheat being ground in a small experimental mill. From 

 the results obtained with fifty-eight different varieties the con- 

 clusion is drawn that the amount of nitrogen in the whole 

 wheat does not afford a measure of the quantity that will be 

 left in the flour. Thus, the proportion of proteins in the flour 

 ranged from 56 -84 to 65-56 per cent, of that origiu.illy present 

 in the grain, while the proportion in the bran showed varia- 

 tions of 25 to 32-7 per cent. Wheats rich in protein yielded 

 flours containing no more nitrogen than those that contained 

 relatively little protein. From the average results obtained 

 with forty-two varieties of wheat it was calculated that the 

 proteins were distributed between the flour, bran and " shorts" 

 in the respective proportions of 61-87, 27-98 and 9-92 per 

 cent. 



DRYING OF YEAST.— Hitherto processes used for dry- 

 ing yeast have inevitably caused the destruction of a large 

 proportion of the living cells and the dried product has had 

 much lower enzymic activity than the fresh yeast. In a process 

 recently described by Herr Hayduck {Zeit. angev:aii. Cliem., 

 1912, XXV, 1179) this drawback is overcome and dried yeast 

 with ninety per cent, of its cells alive is obtained. 



