GRAMINE^. CEREALS 491 



In barley for malting purposes, where the proportion of nitro- 

 genous compounds should be as low as possible, it is essential 

 that the crop should have time to accumulate carbohydrates in 

 the grain in large amount or its value for malting is much reduced. 



While the ear and grains are ripening, changes are going on 

 in the roots, stem and leaves. There is a general movement 

 of water from below upwards and at the same time a transla- 

 tion of useful plastic materials (sugars, amides and proteids) 

 from the lower leaves and stem to the upper parts of the plant, 

 these materials being finally utilised in the formation of the 

 embryo and its store of starch and other reserve-foods in the 

 neighbouring endosperm-tissue within the grain. 



Death also takes place, gradually from below upwards, the 

 roots dying off some time before the grains are ripe. 



Although the ripening changes go on continuously it is useful 

 to notice four stages, known respectively as (i) the milk-ripe, 

 (2) 'CnQ yellow-ripe, (3) ripe, and (4) the dead-ripe stages. 



In the milk-ripe stage the endosperm tissue contains much 

 water and when the grain is squeezed a white milky juice oozes 

 out consisting of the watery cell-sap and numbers of starch 

 grains. Although the lowermost leaves are dead the leaf- 

 sheaths and the blade of the uppermost leaf are still green ; 

 the glumes are also green, so that the whole crop wears a 

 green unripe tint. 



In the yellow-ripe stage, on cutting across or breaking the 

 grain, the endosperm is found to be somewhat tough and kneads 

 like wax. The pericarp of the grain has lost its green colour and 

 the straw has assumed a yellow tint, except at the upper nodes 

 of the stem where the cells are still soft and sappy and contain 

 green chloroplastids. 



In the ripe stage, which in hot weather occurs three or four days 

 after yellow ripeness, the straw is usually of lighter tint, and the 

 nodes which die last are now dead, shrunken, and brown. The 

 grain is harder and firmer. 



