'22 MAIZE 



CHAP. Apex of Grain. 



IV. 



(a) Roof-shaped at one edge, i.e. convex at one and flat at the other. 



(b) Shingled, i.e. overlapping like shingles on a roof. 



(c) Flat or square, corners not rounded at summit. 



(d) Rounded, corners rounded at summit. 



(e) Rostrate or beaked, with long, sharp, tapering projection. 



(/) Mucrouate or pointed, with small, sharp point at summit from embryo side. 

 (g) Dented (only in dent breeds), with an indentation of varying size and 

 form. 



Indentation of Grain. 



(a) Round dimple, rounded or cup-shaped and quite smooth. 



(b) Long dimple dented, i.e. longer than broad, and quite smooth. 



(c) Creased, i.e. edges pressed towards each other, leaving a smill space 



between and the edges parallel. 



(d) Pinched, the edges pinched closely together and projecting upward and 



forward. 

 (c) Rough, with any rough, jagged, or beaked projection from the summit. 

 (/) Bridged, with a fold across the centre. 

 (g) Crumpled, or wrinkled, as in sweet maize. 



91. The Hull. — The hull or outer covering of the ripe 

 maize grain (Figs. 15 and 60) is hard and shiny. It comprises 

 the pericarp of the fruit together with the testa or seed-coat 

 ("with which it is united), and the perisperm, a layer of tissue 

 beneath the testa and surrounding the endosperm (Fig. 15). 

 Of these three tissues the pericarp forms the larger part of the 

 hull of the ripened grain. 



The hull can be easily removed from the aleurone layer 

 for study, by soaking in hot water for about fifteen minutes. 



92. The Aleurone Layer. — Lying immediately beneath the 

 hull, between the perisperm and endosperm, is a tissue com- 

 posed of a single row of comparatively large cells, rather regular 

 and rectangular in transverse or cross section (Fig. 60). This 

 tissue is called the aleurone layer ; it comprises 8 to 14 per 

 cent of the grain. 



Webber (2) has shown that the blue, purple, and black 

 colour of the soft flour and sugar varieties of maize lies in the 

 aleurone layer. In yellow maize, however, the yellow colour- 

 ing matter is not confined to the aleurone layer, but penetrates 

 the endosperm. In some of the red-grained breeds of maize, 

 and in the red-striped Cusco, the red colouring matter is con- 

 fined to the pericarp, which accounts for the fact that red 

 maize is sometimes produced from white seed. 



