REVIEWS 161 



of gooseberry mildew indicates distribution from infected nurseries rather than 

 carriage by wind ; the blister blight of tea failed to reach Darjeeling for at least 

 forty years after its appearance in Assam ; Pythium palmivorum spread centri- 

 fugally from Godavri at the rate of from i to 3 miles per annum, but the spread 

 was always continuous without intervening uninfected areas. Other instances are 

 afforded by the vine and oak mildews, the carnation rust, the coffee-leaf disease, 

 and the hollyhock rust. 



The geographical distribution of various genera supports the same contention 

 that long-distance carriage by air currents rarely occurs. Of the examples cited 

 we may quote that of Uromyces, of which genus 119 species occur in Europe and 

 249 in America ; only four or perhaps six are common to both regions, and these 

 are parasitic on cultivated plants. 



Such evidence suggests that man has played an important part in the trans- 

 mission of fungal pests, on or in living plant material, over long distances — a role 

 that increases with the increased facilities for transport. Mr. Butler points out 

 that once a parasite has been introduced into a new area its extermination is 

 extremely difficult, so that some check on the transport of infected material 

 is becoming more and more essential. 



In this connection the recommendations of the International Phytopathological 

 Conference held at Rome in 191 4 are considered, especially in their relation to 

 India. Briefly, the object of the Convention drawn up was to control the sanitary 

 condition of imported horticultural produce. Certificates would be granted by 

 Government inspectors that the exported plants were free from the diseases 

 enumerated in a list furnished by the importing country. 



The author aptly points out the danger of any attempt to standardise remedial 

 measures which might accrue from official interference. The criticism is advanced 

 that the Convention makes no discrimination between continuous and discontinuous 

 dissemination. Also in view of the marked variation in virulence of the same 

 parasite in different countries, the proviso that only such diseases may be listed 

 by any country as ai t very harmful or destructive is open to grave objection. 



Whilst broadly the author approves of the application of the Convention to 

 India, he offers pertinent suggestions and criticisms of very general application 

 which should be read by all interested in this extremely important subject. 



E. J. Salisbury. 



AGRICULTURE 



Annuaire Internationale de Statistiqne Agricole, 1915 et 1916. Institut 

 International dAgriculture. Service de la Statistique Generate. [Pp. 

 xlix + 949.] (Rome : Imprimerie de PInstitut, 1917. Price 10 frs.) 



Various additions and extensions have been made in the preparation of this 

 new census, which now displays the state of the world's agricultural industry from 

 1907 to 1916 inclusive, making it still more valuable as a standard work of 

 reference. 



The table of contents is given in five languages, followed by ten pages of intro- 

 duction to the 836 tables of statistics, which make the volume up to a thickness 

 of a little more than three centimetres. Preceding them is a notice calling atten- 

 tion to the notation by which the compilers distinguish between official data, 

 official estimates, and private data, and to the quinquennial averages. 



The tables embody statistics of area and population, the classification of areas 

 as productive and non-productive, and the further sub-division of the productive 

 areas according to the type of cultivation. The various crops of the world are 

 II 



