198 The Develojrmeiit of the Grain of Wheat 



unit which will .suffer the minimum of variation during the whole 

 period. 



In the field there will always be a good deal of variation of de- 

 velopment between the central and the secondary shoots, hence the 

 general produce in the field will not show the progressive changes quite 

 so sharply as the experimental material. 



In 1907 one of the wheats was selected from Plot 3 on the Broadbalk 

 Field at Rothamsted, which had grown wheat without manure since 

 1843 ; the variety was Square Head's Master, a typical heavy-yielding 

 weak English wheat. Though the crop on this plot is small, the grain 

 is quite normal. Material was also taken from Plot 10 on the same 

 field, which receives only nitrogen in the form of ammonium salts every 

 year. The grain from this plot shows several peculiarities — it possesses 

 a high nitrogen content and looks strong, but when a baking test of 

 the flour is made proves to be excessively weak, though after storage for 

 some months it gains some strength, without however reaching the 

 normal degree for that variety. The third example was taken from 

 the neighbouring Little Hoos Field and consisted of spring-sown Red 

 Fife, a strong wheat of very different character from Square Head's 

 Master. In 1908 only one wheat was selected, this was Square Head's 

 Master grown on one of the margins of the Broadbalk Field, which had 

 been down in grass some few years before and had also grown potatoes 

 with farmyard manure, so that it may be taken to represent wheat 

 grown under ordinary conditions of farming. 



The actual data obtained are given in the tables in the Appendix : 

 for purposes of discussion they have been thrown into curves, which it 

 will be convenient to consider seriatim for each property determined. 

 The Red Fife was a few days later both in flowering and cutting than 

 the Square Head's Master, but as the march of development was quite 

 parallel for the two varieties, the curves which follow have been drawn 

 for corresponding periods after flowering instead of for the actual dates 

 of sampling. 



The weather conditions prevailing during the two seasons 1907 and 

 190^ were in marked contrast; in 1907 the summer was generally 

 overcast and cloudy, with low temperatures and frequent rains ; in 

 1908 the early part of the summer was hot, and though there was rain 

 in July, August was a fine hot month up to the completion of the 

 harvest. 



The following table indicates how different was the weather in the 

 two years : 



