THE BARLEY CROP. 97 



the term isotheral. Some of our cultivated plants 

 those for forage purposes, for instance thrive best where 

 the climate is equable, where the variation between the 

 winter and summer temperature is comparatively small, 

 and where extreme temperatures are not met with ; others 

 again, those cultivated for their seed, whether as articles 

 of food or commerce, generally require a more constantly 

 higher temperature at the time of their maturity than at 

 any other, and thrive best where they can secure these 

 conditions, so necessary for their reproductive powers. 



"We have many places in our own country where barley 

 cannot be successfully cultivated ; yet we find it grown in 

 Shetland, lat. 61, and in the Faroe Islands, lat. 61 to 

 62 15'. According to Berghaus, in Western Lapland, the 

 limit of its cultivation is near Cape North, 70 lat., the 

 northern extremity of Europe. In Western Russia, on the 

 shores of the White Sea, it lies between the parallels of 

 67 68' on the western side, and about 66 on the eastern 

 side, beyond Archangel. In Central Siberia its limits are 

 between lat. 58 and lat. 59. Such is the sinuous curve 

 which determines the cultivation of barley, and all the 

 other cereals are obedient to the same laws. A little fur- 

 ther north all cultivation of vegetables ceases, at least so 

 far as articles of food are concerned ; the people live on the 

 products of the cattle, as in the higher regions of the Alps 

 and other mountainous districts, or by hunting or fishing, 

 as their conditions may determine. But beyond the limits 

 of barley cultivation there occurs a narrow and undeter- 

 mined zone, in which certain early potatoes are successfully 

 grown, and where the snow does not cover the ground for 

 a sufficient length of time to prevent the growth of some 

 of those vegetable substances low in the scale of nutrition, 

 but still available as food for man, such as fruits, lichens, 

 bark, roots, &c. As the introduction of the potato is, in 

 comparison with barley, recent in those regions, it almost 



