186 Mr. A. Mallock. Growth of Trees, with a Note on 



reducing substances leading to carbohydrates, and discusses the conditions 

 favourable for such condensations. The energetics of such a system are 

 treated of in this section, and the effects of general or local concentration are 

 considered. The equilibrium point in reversible reactions is shown to be 

 dependent on concentration. 



In the concluding section a general reversible reaction is described as a 

 result of which formaldehyde rises in all intense reactions of light upon 

 substances of bio- chemical origin. This reaction in presence of excess of light 

 is an interesting reversal of the process by which all organic matter has been 

 built up from inorganic sources. 



The bearing of this process upon the germicidal action of sunlight, and the 

 destruction of living organisms by ultra-violet light, is discussed, and it is 

 pointed out that the simple organic products so formed are incompatible with 

 the life-processes of living organisms, and so lead to their destruction. 



Taking such a reaction as travelling in the reverse direction, it is shown 

 that the building up of organic matter from inorganic must have been a 

 necessary precedent to any existence of living organisms on the earth, and 

 that all accumulations of reduced substances possessing stores of chemical 

 energy must have arisen in this manner from storage of the energy of 

 sunlight. 



Growth of Trees, ivith a Note on Interference Bands formed by 

 Rays at Small Angles. 

 By A. Mallock, F.R.S. 



(Received December 1, 1917.) 



But little is known about the growth of %vood, little that is as to the times 

 and rates at which the growth takes place. 



When a tree is cut down, its age and growth in a season can be determined 

 by the number and dimension of the annual rings, at any rate where the 

 annual rings exist and are well marked ; though it not infrequently happens 

 that the rings are alternately weak and strong, so that some doubt may arise 

 as to whether there have not been two periods of growth in one year. 



Many tropical trees do not show annual rings at all, and in their case the 

 age of the tree and its growth in a year cannot be found from an examination 

 of a section. 



It would, I believe, be an assistance in Forestry could some fairly simple 

 means be found for measuring rapidly, i.e., in a few days, or even weeks, the 



