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each, both on account of the number of parasites concerned and the economic 

 importance of these plants. 



For each species of parasite the writer describes its distribution, the symptoms 

 of the disease, the life history and methods of treatment. 



The work concludes with a bibliography of some six hundred references 

 classified under the chapter headings. 



The production of a work treating especially of the plant diseases of India is 

 the more welcome in view of the large number of indigenous fungi which produce 

 them, and we shall look forward to a further volume in which the parasites of 

 the forest trees are to be considered with pleasurable anticipation. 



It may be added that the printing and illustrations are excellent, whilst the 

 index is far superior to that of most books of this character. 



E. J. Salisbury. 



I. Plant (Ecology and its Bearing on Problems of Economic Importance in 



India. By R. S. Hole, F.C.H., F.L.S., F.E.S. [Pp. clvi-clxvii and 

 Plates V.-X. Jour, and Proc. Asiatic Soc. Bengal, Vol. XIV., 1918.] 



II. Recent Investigations on Soil Aeration, with Special Reference to Agri- 

 culture and Forestry. By A. Howard and R. S. Hole. [Pp. 415-40, 

 Plates XXIV.-XXIX.,and Figs. 1-6. Agric. Jour, oj India, Vol. XIII., July 

 1918.] 



The value of cecological methods of investigation as a means of solving economic 

 problems is only just beginning to be realised, but, having regard to the infancy 

 of this branch of botany, the results already achieved are the earnest of its coming 

 importance for practical agriculture and forestry. 



Mr. Hole, in his Presidential Address before the Asiatic Society of Bengal, 

 performed a distinct service in calling attention to the part that oecology and 

 cecological methods have already played in solving sylvicultural and other economic 

 problems in India, and it is to be hoped that the authorities are fully alive to the 

 need for both moral and material encouragement for research on these lines 

 which the Indian Forest Service is so eminently fitted to undertake. 



An excellent example of such work, carried out by the author, is that con- 

 cerned with the reproduction of Sal {Shorea robusta), dealt with in Part II. of the 

 second-named paper. The natural regeneration of the forests of this valuable 

 timber tree is often either delayed or even almost inhibited by deficient soil- 

 aeration. As a consequence of the latter, root development is retarded, so that 

 with the advent of the dry season from September ta June the root systems of 

 the seedlings have not reached a sufficient depth to withstand the drought and a 

 high mortality ensues. The results of cecological experiments have not only 

 established these facts, but have also shown that the ill effects can be remedied by 

 burning the raw humus and by clear-felling in small patches. 



The attacks of Polyporus shorecz appear to be particularly associated with the 

 same adverse conditions, and the soil-aeration factor is probably also of first 

 importance in the regeneration of many other timber trees of India. Mr. Howard, 

 in the second paper, after summarising some of the recent work on this subject, 

 suggests that soil aeration may be largely responsible for the differences in quality 

 of barley, tobacco, and cotton. 



Mr. Hole (I.) emphasises the importance of the study of natural plant com- 

 munities as revealing conditions of the habitat and thus indicating the most 

 suitable methods and species for a given locality ; a sylvicultural application of 



