88 THE COTTON PLANT IN EGYPT CH. iv 



whenever and wherever possible, on physico-chemical 

 possibilities. The author's own opinion favours such 

 readings of the experimental text, if only as a refuge from 

 disguised vitalism. Lest such opinion be made an 

 accusation, it may be well to point out that many 

 recorded phenomena will not yet yield to the point of 

 such hypothesis. One irreconcilable of this order is the 

 striking " sleep-movement," which is exhibited by all 

 leaves throughout the year, and even by the seed-leaves. 



The organic factors of the environment, such as fungoid 

 and insect pests, together with the flora and fauna of the 

 soil, cannot be discussed within these limits. The fungi, 

 excepting "Sore-shin," are of negligible importance in 

 Egypt, though Colletotrichium gossypii, Mycosphcerella 

 gossypina, and Meliola spp. are extremely common. The 

 insects, conversely, are of great economic importance, 

 though the blame for many of their reputed crimes really 

 lies at the feet of the plant, particularly in respect to the 

 boll-worm. Some such confusions have already been 

 noted in passing, and it is curious to note that a mild 

 attack of cotton-worm, through diminishing the water- 

 strain, may actually increase the yield by prolonging the 

 flowering-period. 



The soil flora, imperfectly understood, must be left 

 untouched by us. In soils of the Nile Valley the 

 geological aspect is superior to the chemical one ; texture, 

 and hence water-content (frequently complicated by 

 "salting") is more important than mammal mixtures. 

 The author's colleague, Mr. F. Hughes, has shown con- 

 clusively that the cotton-crop of latter-day Egypt is rarely 

 limited in Blackman's sense by the chemical com- 

 position of the soil. Water, always sufficient, but never 

 excessive, is the principal need of the crop ; 24 and the 

 desired balance between deficit and surplus is struck only 

 by accident as yet. 



