i8 F. H.W.GREEN 



increase in the annual PWD, combined with human-induced modification 

 of the natural surface, can often be sufficient to start spectacular erosion of 

 bog which had developed during a period when the annual PWD was 

 insignificant in amount. 



REFERENCES 



Alvin, p. de T. (i960) Moisture stress as a requirement for flowering coffee. Science, 

 132, No. 3423, 354. 



MoHRMANN, J.C.J. (1959) A tentative survey of the water deficiencies in Europe and 

 the need of (supplemental) irrigation. Report of the Conference on Supplemental 

 Irrigation, Copenhagen, 1958, 25-34. (Published by the Institute for Land and 

 Water Management Research, P.O. Box 35, Wageningen, Netherlands.) 



