ASH CONSTITUENTS OF FOODS 83 



and turnip tops, etc.), are all comparatively rich in 

 "lime," while cereal grains (especially maize and rice) 

 and potatoes are poor in this constituent. If the 

 drinking-water is hard, this may supply to some extent 

 the deficiency in the food. 



Roots, meadow and clover hay, leguminous straws, 

 and oil-cakes are comparatively rich in "potash," while 

 cereal grains are rather poor. 



Many foods contain insufficient soda for the require- 

 ments of the animal body, and this is best supplied in 

 the form of rock salt, so that the animal may regulate the 

 quantity at will. Common salt should not be given to 

 pigs or poultry, especially with sharps, which are 

 slightly acid, otherwise some of them may suffer and 

 even die from salt-poisoning. 



XIII. VARIATION IN COMPOSITION OP PLANTS. 



The chief causes which are responsible for variation 

 in the composition of plants are : ( I ) climate ; (2) variety ; 

 (3) manuring ; (4) stage of ripeness when harvested ; 

 (5) weather conditions during harvesting and storage. 



Climate. It is well known that Canadian and 

 Russian wheats are richer in gluten and poorer in 

 carbohydrates (starch) than British wheats, due to the 

 shorter growing season and hotter climate in Canada 

 and Russia than in Britain. 



Flax seed grown on the European continent is 

 richer in oil than that grown in Ireland. 



Grieg and Hendrick (Aberdeen) found with refer- 

 ence to oat straw that it varied in different counties, 

 e.g.) Morayshire straws were richer in albuminoids and 

 lower in fibre than those under trial in Ross and 

 Cromarty. In the former case the straw of Potato 



