CHAPTER II 



THE GRAIN : STRUCTURE, COLOUR, AND OTHER CHARACTERS 



A GRAIN of wheat, often spoken of as a " seed " by farmers, is a nut-like 

 fruit termed by botanists a caryopsis, a name first used by Richard. 



It contains a single seed or kernel enclosed within a thin shell ; the 

 seed, however, instead of being free as in many nuts, is adherent to the 

 inner wall of the pericarp or shell, and the two cannot be separated readily. 



As indicated later, the grains of different kinds of wheat vary con- 

 siderably in size, form, and colour : they nevertheless all resemble each 

 other in fundamental structure, being fruits with thin- walled pericarps, 

 each containing a single seed, the latter consisting of four_j)arts, viz- 

 (i) the seed-coat or testa, sometimes termed the spermoderm ; (2) the 

 embryo or young wheat plant ; (3) the nucellar layer ; and (4) the endo- 

 sperm or floury part a thin-walled parenchymatous tissue stored with 

 food for the nutrition of the embryo when germination commences. 



From careful dissection of several grains and weighing of the separate 

 portions the embryo was found to weigh from 2-8 to 3-5 per cent of the 

 grain ; the pericarp, seed-coat, nucellar layer, and aleuron layer from 7-8 

 to 8-6 per cent ; the rest, or some 87 to 89 per cent, being the endosperm- 

 parenchyma, containing starch and gluten. 



Ordinary white flour consists chiefly of the finely ground endosperm, 

 the so-called " milling offals " consisting of the broken pieces of pericarp, 

 seed- coat, aleuron layer, and the embryo, the latter being usually separated 

 from the other portion of the grain. 



The Pericarp. The dorsal surface of the pericarp of a grain of wheat 

 is smooth and rounded, the opposite or ventral side having a characteristic 

 inward fold or furrow called the " crease " by millers. 



At the base is a small wrinkled patch the part of the pericarp which 

 covers the embryo plant within. The apex is clothed with a number of 

 short stiff hairs, which curve inwards towards a common point, and form 

 the " brush " of the grain. The surface covered by the " brush " slopes 

 slightly to the furrow side, and is somewhat triangular in outline ; among 

 its hairs the remains of the styles are found. 



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