88 WHEAT PRODUCTION IN NEW ZEALAND 



But, besides the error ascribable to variation in soil 

 in a single season, there is a still larger probability of 

 error due to variations between season and season. This 

 fact is, however, so generally recognised that to enlarge 

 upon it is unnecessary, except to point out that compara- 

 tive trials carried out during successive seasons must be 

 carried out on the same class of land if any conclusion 

 is to be arrived at. It is obvious that a trial made on 

 heavy soil in a dry season and on light soil in a wet 

 season will tend to give the same result, and the experi- 

 menter might say, "The result is reliable, for I have 

 proved it on two different classes of land during two 

 different seasons." In reality, the result might be mis- 

 leading as regards both heavy and light land in a normal 

 season and certainly is inconclusive for heavy land in 

 wet seasons, and light land in dry ones. The prime 

 necessity of carrying out a series of experiments during 

 successive seasons only on lands of the same type seems 

 to be the weightiest argument in favour of a soil survey. 



5. Details of Experimental Work. 



Having described the principles of single ear selection, 

 and the necessity of replication of experiments in order 

 to arrive at reliable results, the details of the method of 

 experiment may now be described. It was decided to com- 

 mence work on the varieties commonly grown in the 

 country, on the assumption that these were best suited to 

 it, as having stood the test of half a century of culti- 

 vation here while other varieties had been tried and 

 rejected. The varieties dealt with, were, therefore, Hun- 

 ter's or Red Chaff, White Straw Tuscan, Solid Straw 

 Tuscan, Velvet, and Pearl. The experience with Hun- 

 ter's will be described, as it has produced the most 

 noticeable results. 



Some hundreds of heads differing in appearance were 

 selected from a normal crop, and these were reduced by 



