3 o2 SCIENCE PROGRESS 



was situated, and so to provide for each year a set of standard 

 data. By linking up small observing-stations in outlying 

 districts to the main one, with observers (not necessarily skilled) 

 in charge of them, these records might be made to show the 

 state of the crop over a whole continent. Such a presentment 

 in numerical or graphic form, with defined precision, day by 

 day, would in itself be of more than casual interest, but its 

 value obviously does not remain at the level of mere crop- 

 reporting. After a few years of such data had accumulated, 

 and as the connection of their variations w r ith conditions of the 

 environment were worked out, they could be used for crop- 

 forecasting. Much of the life-history of any plant is recapitula- 

 tion of previous events, and this is remarkably so in the case 

 of irrigated cotton, where practically the only uncontrollable 

 variant in the environment is temperature. Whether the cost 

 of organising such a system would offer a profitable return in 

 the form of certainty and security remains to be seen. Much 

 of the cost would be economised in the lessened need for 

 travelling expert reporters on crop conditions, and the cost 

 need not be enormous when administered as a branch of the 

 normal activities of an experiment station. 



The systematic records of existing crops having provided 

 the investigators with definite information as to the reactions 

 which the crop is making with the environment, the task of 

 analysing these reactions becomes prominent. It may not 

 always be practicable to attempt to withhold the incidence of 

 some limiting factor throughout the season, under the conditions 

 which obtain in the average fields of the country, but there 

 would seem to be many cases — even in an old-established 

 country like Egypt — where control can be exerted for a few 

 days longer than would be practicable by rule of thumb. 



This leads on to the classification and study of environ- 

 mental factors in two fairly distinct groups : controllable 

 factors and uncontrollable factors. 



Of the controllable factors the chief are the soil and water, 

 with insect pests, while atmospheric temperature and humidity 

 may be modified to some extent by the spacing of the plants. 

 In the matter of water-factors our views have undergone 

 considerable revision since the deep draught of the cotton root 

 was recognised, and the changes in water-content of the soil at 

 depths down to three metres are now known to bear very 



