363 



as bushels or pounds, since the absohite crop depends so much upon 

 the soil, the manuring, the cultivation, the thickness of seeding, and 

 other details. On the other hand, the crop of one season must have 

 some relation to the crop of the preceding season by reason of the 

 inherited tendencies of the seed from which it was raised. The cli- 

 ,, „ rainfall or useful moisture , rainfall or nutriment 



matic factors te.,,perature^.Fh^ ^"^ ^iTH^hi^ " 



are, as shown by Linsser, the data that must be compared with the 

 resulting harvests. 



(4) It is evident that the (juestion of the effect of climate on a 

 given crop in the past is not so important as the prediction of what 

 crop will be harvested from a given field already planted. On this 

 point I have given all the illustrations that I could find, especially 

 in Chapter XII, showing how from an analysis of a sample at any 

 given date one should be able to predict the resulting crop. The 

 result can be made correct to within 10 per cent, if we allow for the 

 ordinary average irregularities of the clitnate, a statement of whose 

 extent can easily be made up from meteorological records. As to 

 extraordinary irregularities of climate w^hich can not be foreseen, I 

 remark : 



(a) First of all the effects of excessive droughts at each stage of the 

 plant can be estimated from the experimental data given in Part I, 

 and will be found to harmonize as well as could be expected with the 

 results of actual experience as given in Part II : 



(h) The effect of severe unusual droughts, or heat, or cold, or mois- 

 ture are ordinarily felt over relatively small portions of the country, 

 so that the average result is small in comparison with the whole 

 crop available in the country; for instance, in 1890, in Kansas 

 and Nebraska the corn harvest was one-half of its usual amount and 

 almost the same in 1887, reckoning, of course, the yield per acre, 

 but this and the corresponding small yields in a few other States 

 represent only an inapiireciable percentage of loss to the country at 

 large. 



(5) The studies of the effect of climate on the daily development 

 of sugar in beets, sugar cane, or sorghum, or on the nutritious harvest 

 of grass and cereals has shown the approximate best dates for harvest- 

 ing these crops. 



(6) The studies of the j^hysiological importance of the leaves of 

 beets will eventually show whether these should be trinnned or how 

 they should be treated in order to stimulate the production of sugar. 

 As the pruning of hop vines and grapevines stimulates the ripen- 

 ing and increases the amount of the crops, and as the plucking of 

 the tassels from the maize apparently increases that crop, and as the 

 plucking of the flowers and balls from the potato vines increases the 

 growth of the tubers, so doubtless in many other ways the methods of 



