t 876 ] 



APPENDIX A. 



Add the following to para 205 (p. 163) : 



Sap usually contains about 4 grammes of solid in solution to every 

 litre. The water, therefore, in which the plant food is dissolved 

 should .contain less,than?.4 grammes of soluble matter per litre, that 

 endosmosis may v go on faster than exosmosis. Excessive manuring 

 with soluble manures, results in exosmosis going on faster than 

 endosmosis, and plants getting dried and burnt up, If horse-dung 

 and horse-urine, for instance, are heaped up round the base of a large 

 mango or other tree, the tree will perish in a few months. 



206, Quantity. The proportion of moisture imbibed and trans^ 

 fjired by a leguminous crop during the whole period of its growth lias 

 been determined by actual experiments to be about 280 times the 

 weight of the dry matter of the crop; whrle in the case of cereals the 

 proportion is about i : 320. But one crop differs from another, 

 and even one variety of one crop^differs from another variety (e.g. 

 aus and aman paddies) very much in this respect. Roughly speaking 

 i : 300 may be taken as the average for crops during the cold 

 weather (which is the result of European experience) and i : 1000 

 for the hot weather crops of this country. But as hot weather crops 

 can depend chiefly on rainfall, even in a bad year, the maximum 

 requirement of crops of irrigation water may be put down at 

 300 times the dry weight of the crop. Suppose an acre of wheat 

 including straw weighs 3 tons. The dry weight of the crop is 

 about 2\ tons. The maximum requirement of irrigation water for 

 this crop is (2^ x 300) 750 tons of water or nearly 200,000 gallons. 

 A, don lifting 10,000 gallons of water per hour, or 80,000 gallons 

 per day is found in practice to be able to irrigate an acre of wheat 

 in one day ; and two irrigations are found ample for the wheat crop 

 even in the worst season. Thus the maximum quantity of irrigation 

 Water required for this crop, as theoretically determined agrees very 

 nearly with what is actually allowed in practice. But there are extreme 

 cases of peculiar habits of plants. TheCicer arietinum, the Panicum 



