146 SCIENCE PROGRESS 



With regard to pollution, the forest litter and humus would doubtless 

 serve as a filter for the flood water from the higher ground, but with 30- 

 90 per cent, of the latter devoted to grazing we fail to see how the presence 

 of the woodland belt would in any way mitigate the not infrequent pollution 

 to which the author refers, viz. the presence of the dead bodies of sheep 

 in the streams feeding the reservoirs. With respect to the financial aspect, 

 very little data is given, but from such as is available it would appear that 

 the pre-war cost of planting was from £B>-£i2 per acre, figures which would 

 need to be more than doubled at the present day. The accumulated debt 

 on this expenditure and the capitalised value of the lost grazing rentals would 

 represent a considerable sum, and even assuming that the present high 

 prices of timber are maintained, it is open to doubt whether Scots pine 

 would show a cash profit, though Douglas fir might well do so, but its 

 growth would be restricted to sheltered spots. 



The author's statement that " there is one means by which water-catch- 

 ment areas can be effectually guarded against pollution and at the same 

 time be put to a profitable use, and that is afiorestation," may then perhaps 

 be regarded as rather optimistic. 



But the argument for such afforestation rests on the general soundness 

 of the policy and cannot be gauged entirely in terms of the cash return. 

 A national reserve of home-grown timber is undoubtedly necessary, and its 

 location here, as the author shows, would bring with it advantages the actual 

 monetary value of which it is not easy to estimate. E. J. S. 



The Fungal Diseases of the Common Larch. By W. E. Hiley, M.A. [Pp. 

 xi-f 204 with 73 plates and diagrams.] (Oxford : at the Clarendon 

 Press, 1919. Price 12s. 6d. net.) 



This work, emanating from the Oxford School of Forestry, deals historically 

 and critically with all the undoubted fungal diseases of the common larch, 

 and incorporates the results of investigations, on some of the commoner of 

 these diseases, undertaken by the author, at the instigation of Sir William 

 Schlich, and with the assistance of grants from the Development Com- 

 missioners and the Interim Forestry Authority. 



The introduction deals with the structure of the normal plant; the 

 larger portion of the book is concerned with the individual diseases, their 

 symptoms, the method of attack of the causative fungus, and also with 

 the special means of preventive action. 



Reasons are given for the view that large larch-cankers are caused by 

 infection passing to the main trunk from a dead branch on which the canker 

 fungus is growing saprophytically, and it is suggested that dead branches 

 and branches that are likely to die should be cut off from young trees. Only 

 experience can show whether this is an economical proceeding. 



In view of the prevalent idea that calcareous soils increase the liability 

 to canker, one is disappointed at finding no mention of this theory, especially 

 as the author advocates growing larch mixed with beech. 



The experiments on pp. no and in do not seem to prove that bacteria 

 are responsible for the suppression of the heart-rot fungus in unsterilised 

 soil cultures, and it is difficult to understand the ground on which it is 

 stated that soils f. and g. both arable (see pp. 109 and in) contain no 

 organised remains. 



The views, here expressed, that the heart-rot fungus {Fames annosus) 

 and the honey fungus are unable to enter uninjured roots seems well 

 founded, and the discussion as to methods of treatment helpful. In the 

 case of the honey fungus, however, treating stumps with sulphuric acid 

 seems rather drastic, and some evidence of the efficacy, in actual practice, 

 of infecting healthy stumps with harmless fungi would have been welcome. 



