Agricultur, Horticultur, Forstbotanik. 139 



The author sums up his results under the following general 

 conclusions : 



"1. The Proportion of phosphoric acid and of potash in the ash 

 of any given plant varies with the amount of these substances 

 available in the soil, as measiired by the response of the crops to 

 phosphatic or potassic manures respectively. 



2. The extent of the Variation due to this cause is limited, and 

 is often no greater than the variations due to season, or than the 

 other variations induced by differences in the supply of non-essential 

 ash constituents — soda, lime, etc. 



3. The fluctuations in the composition of the ash are reduced to 

 'a minimum in the case of organs of plants, which, like the grain of 

 cereals, or the tubers of potatoes, are manufactured by the plant 

 from materials previously assimilated. 



4. The composition of the ash of cereals is less affected by 

 changes in the composition of the soil than is that of root crops like 

 swedes and mangels. 



5. The composition of the ash of mangles grown without manure 

 on a particular soil gives a valuable indication of the requirements 

 of the soil for potash manuring. Similarly the phosphoric acid requi- 

 rements are well indicated by the composition of the ash of unmanu- 

 red swedes, though in this case determination of the citric acid soluble 

 phosphoric acid in the soil gives even more decisive information. 



6. Pending the determination of phosphoric acid and potash 

 „constants" for some test plant occurring naturally on unmanured 

 land the interpretation of soil-conditions from analyses of plant-ashes 

 is not a practicable method by which chemical analysis of the soil 

 can be displaced." R. H. Lock. 



Hall, A. D., The Book of the Rothamsted Experiments. 

 (London, 1905 8o. XL, 294 pp. ill.). 



The author, who succeeded Sir J. H. Gilbert as director of the 

 Rothamsted Experiment Station, has in this book collected in a con- 

 venient form the results of all the work of the Station since its foundation. 



He begins with a chapter on the sources of the nitrogen of Vege- 

 tation, one of the earliest subjects investigated at Rothamsted. Then 

 follow chapters on the Meteorological Records, and the Soils of the 

 Experimental Fields. 



The greater part of the book consists of a systematic discussion 

 of the experiments on the continuous growth of Wheat, Barley, Oats, 

 Root-crops, Clovers and Hay; and on the grow^th of crops in rotation. 

 Each crop is discussed in a separate chapter, at the end of which 

 the results are summarised, and a list given of all the original publi- 

 cations on the subject. 



The important work on Nitrification and Drainage Waters, and 

 on the Feeding of Animals, is dealt with in tAVO chapters, and the 

 book concludes with a chapter on such min r subjects as Sewage, 

 Malting, Ensilage, and the Milling products of Wheat. 



Practical conclusions, which appear to be drawn partly from the 

 results of the experiments and partly from the author's general 

 experience, are given at the end of each chapter, in order that the 

 book may be of use nut only to the Student but also to the practical 

 agriculturalist. 



The point of each experiment is illustrated by photographs or 

 diagrams. Mr. R. Warington has written an introduction, in which 



