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SOME PROBLEMS OF ECONOMIC BIOLOGY 

 IN EAST AFRICA (KENYA COLONY) 



By W. J. DOWSON, 

 Roijal Horticultural Society's Gardens, Wisley. 



(With 1 Text-figure.) 



L Introduction. 



The effect of meteorological conditions on the relations between the host 

 and its parasites has received little attention at the hands of the patho- 

 logist, but in a country like East Africa it supplies the key to the solution 

 of the problem concerning the severity of attack. 



For an understanding of the problems which confront the economic 

 botanist and the agricultural entomologist it is essential to gain some 

 knowledge of the physiograjihical and climatic conditions of this part 

 of Africa, conditions so varied in extremes as to affect both host and 

 parasite to a marked degree. The Kenya Colony is situated between the 

 4th parallel N. latitude and the 4th parallel S. latitude, has an area nearly 

 twice that of the United Kingdom, but a population which cannot amount 

 to more than 5 millions. The equator passes through the northern slopes of 

 Mount Kenya, the glacier-covered peak of which rises a few miles south to 

 a height of 17,000 odd feet. 120 miles due south of Kenya and j ust within 

 Tanganyika Territory is Mount Kilimanjaro, whose summit rises 19,000 

 odd feet above sea level; and 120 miles W.N.W. from Kenya, and on the 

 boundary line separating Uganda from East Africa hes Mount Elgon, 

 14,000 feet in height. The snow line is situated at an altitude of 15,000 feet 

 above sea level. 



These numbers are apt to give an exaggerated impression of altitude, 

 for the height of all the Central African mountains from the general level 

 of the surrounding country is considerably less because they rise from 

 plateaux and uplands of 5000 to 7000 feet. Thus the highest point of 

 Kenya from the general level of the surrounding country is, roughly, 

 11,000 feet. 



Running north and south right through the country is the Great Rift 

 Valley, one branch of which stretches from Lake Rudolph in the north 



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