364 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



" The Spirit of the Soil." By G. D. Knox. 8vo. xiii -f 242 pp. 

 (Constable, London, 1915.) 2s. 6d. net. 



We have enjoyed reading this book immensely. It is " an account 

 of the nitrogen fixation in the soil by bacteria and of the production 

 of auximones as promoted by bacterized peat," and a foreword by 

 Prof. Bottomley, the originator of bacterized peat or " humogen," 

 tells us that he takes full responsibility for the statements contained 

 in the book. It puts the case for bacterized peat in a fashion worthy 

 of the effort of an eminent Counsel determined to obtain a verdict 

 for his client, and withal convinced of the Tightness of his cause. It 

 has all the merits and all the faults inseparable from good special 

 pleading, and it deals in a lucid and readable manner with many 

 aspects of the subject, which often branches off into difficult and 

 technical matters. We hope that the book will be widely read, and 

 that its readers will suspend judgment until they have secured some 

 of the peat and tried it carefully outdoors themselves, taking care to 

 avoid the errors into which some of those whose success is reported 

 have apparently fallen in making their experiments. 



We wish the author were a horticulturist — we think he cannot be, 

 or he would have avoided such names as Cordyline Dracena, Brussel 

 Sprouts, Balsam Impatiens, Veitchii Calanthe, and the like — and he 

 would then, with his evident scientific knowledge and clear grasp of 

 scientific methods, have been able the better to see the many pitfalls 

 into which experimenters with living plants, especially in the open 

 ground, may fall. 



We have referred in another place to the value of bacterized peat, 

 and need do no more than state here that not all the results have been 

 so favourable to the use of " humogen " as have most of those to 

 which the author refers. We cannot, however, refrain from quoting 

 one experiment which is relied upon to show the value of bacterized 

 peat. It is on p. 146. Four potatos were put into a box 15J inches 

 by 6 inches by 4 inches, containing sterilized moss. This moss was 

 first soaked in humogen extract and the plants were watered from 

 time to time with the same (nothing is said of the quantity used, the 

 original weight of the tubers, the result of growing four tubers of the 

 same variety and weight in sterilized moss merely watered with a 

 weak solution of earth salts). At the end of some time (not stated) 

 the tubers were taken out and weighed, the total produce being 2 lb. 

 ioj oz. Now, surely there is nothing remarkable in this. The 

 space was small truly, but if one compares the yield with that obtained 

 from four tubers grown in ordinary good soil one cannot but be struck 

 with its smallness. In the Wisley trials, e.g., reported on pp. 292-304, 

 weights obtained from 20 tubers of each of many varieties may be 

 compared with profit. Bacterized peat may well prove to be a valuable 

 manure, but " experiments" such as this will surely not, convince 

 any thinking horticulturist, though to see a box packed with many 

 potatos " all grown from four " may be an exciting spectacle for the 

 uninitiated. 



