28 FLOURS. 



(21) Rye Flour. 



The anatomical structure of the rye grain closely resembles that 

 of wheat. The principal diagnostic features of the flour are to be 

 found in the appearance of the hairs and in the size and characters 

 of the starch grains. 



The hairs of rye have about the same shape as those of wheat ; 

 they differ, however, in the lumen, for in the rye this gradually 

 enlarges from apex to base, whereas in the wheat it is nearly linear 

 in the upper part, and then suddenly enlarges and becomes bulb- 

 shaped at the base. 



Rye starch, as already observed, is generally larger than wheat 

 starch, and there are always some grains that possess a distinct 

 stellate hilum. It must not be imagined that all the grains will 

 exhibit this feature, but it is safe to assert that in every sample 

 of rye starch there will be found a notable proportion that show it. 

 Rye starch is also characterised by the presence of a perceptible 

 number of small bell-shaped grains. 



There is also a difference in the shape of the lignified cells of the 

 hypoderrna; these are usually longer than the transverse cells, 

 whereas in wheat they are shorter. The transverse cells are also 

 more frequently rounded at the ends, and have thinner walls than 

 tney have in wheat. 



The diagnostic characters of rye flour are : 



(a) The hairs with less abruptly enlarged lumen and thinner 

 ivalls than in wheat. 



(b) The transverse cells which have thinner walls and fewer pits, 

 they are mostly shorter than the hypoderma cells, and often rounded 

 at the ends, where the walls are also rather thicker. 



(c) The starch grains which are rather larger than those of wheat 

 and often show a stellate hilum and concentric stria. 





