23 



this season of its growth the phmt really needs less water than before, 

 but still its roots have the same power of absorbing water, and if the 

 sap is thus diluted there results a seed or fruit that is heavy with an 

 excess of water. Of course this water will dry out, if it has an 

 opportunity, after the harvest, but if it has no opportunity, on account 

 of damp weather, it Avill remain in the seed and render the latter more 

 subject to injury from fungi, whose spores are always floating in the 

 air seeking a moist nidus or resting place favorable to their growth. 

 Such moist seeds give a heavy, green harvest, but a light dried crop. 



Thus it happens that the distribution of atmospheric heat, and 

 moisture, as to time, is quite important in its effect on the local harvest. 



Apparently the time of ripening of the harvest depends wholly 

 upon the chronological distribution of water and sunshine, but the 

 quantity and quality of the harvest, which are the important practi- 

 cal results to the farmer, depend upon the nutrition carried into the 

 plant by the water that is absorbed by the roots. 



IRRIGATION. 



The determination of the right time for irrigation and of the 

 proper quantity of water, in order to produce the best crop in soil 

 of a given richness is the special problem of those planters who 

 depend mostly upon irrigation for successful agriculture. In general 

 it may be said that our ordinary seeds have long since been selected 

 and acclimatized with a view to success in a climate where abundance 

 of moisture is available at the proper season. Hence our crops are 

 not so likely to be injured by excess of rain as by deficienc}^ or 

 drought. Therefore in almost every section, from the Rocky Moun- 

 tains to the Atlantic, the highest success can only be attained by mak- 

 ing provision for artificial irrigation in times of drought. The exact 

 times and quantities of irrigating water depend upon the seed, the 

 soil, and the evaporation, which latter is due to dryness of the air, the 

 velocity of the wind, and the character of the soil ; but when artificial 

 watering or irrigation is needed to supi^lement natural rain one must 

 seek to ai^proximate as closely as practicable to the conditions 

 presented in the countries where the seed originated, and' especially 

 the conditions presented during the seasons in which the given seed 

 produced the best crops. 



IMPORTANCE OF CLIMATIC LABORATORIES. 



The studies that we are entering upon are greatly facilitated by 

 experiments on a moderate scale under conditions that are under the 

 control of the investigator, and free from the irregularities of open- 

 air agriculture. The laws of nature can only be found out by ques- 

 tioning nature, as it were, by means of test experiments. Our present 



