102 BIOLOGICAL PROBLEMS 



themselves, and make no effort to control them ; 

 instead, we grow crops that suit the climate. Thus 

 the crop map of the country corresponds fairly closely 

 with the climate map, e.g. grass tends to be grown 

 in the wet west and north-west, and wheat and other 

 grain crops in the drier eastern and southern counties. 

 The climate largely determines the distribution of 

 crops. 



But climate does not altogether settle crop produc- 

 tion. The map showing yield of wheat is very dif- 

 ferent from that showing distribution. The highest 

 yields of wheat are obtained in Lancashire, North- 

 umberland, Anglesey, and Kent. In many of these 

 cases the wheat is rather a special crop grown under 

 some special conditions or by some special farmers, 

 and there is some particular reason why it should be 

 better than usual. 



But our common crops are not single, homogeneous 

 individuals: they comprise a large number of varieties, 

 which differ considerably in their environmental re- 

 quirements. Barley furnishes very good examples: 

 the Archer types, with a stiffer straw and longer 

 growing period, are later ripeners, and therefore 

 better suited to cold, wet conditions than the Cheval- 

 liers, which ripen earlier, and therefore do better in 

 warm conditions and light soil, 1 while on rich soils 

 the Goldthorpe varieties flourish best. The Potato 

 variety of oat, one of the most popular in Scotland, 

 does badly in the south and east of England ; Black 

 Tartarian oats do well in the southern counties on 

 the chalk land, and Goldfinder in the western coun- 

 ties. Yielder and Record oats do well on rich soils 

 in moist climates, and Black Tartarian and Sandy 



1 See an interesting paper on this subject by Mr. E. S. Beaven, /. Farmers 

 Club, December, 1905. It should be pointed out, however, that the Archer 

 types do well in the warm, dry Eastern counties. 



