38 FLOURS. 



(26) Buckwheat Flour. 



The fruit of the buckwheat (Fagopyrum esculentum, Moench) is 

 an achene. The pericarp is composed of (1) An epidermis con- 

 sisting of a single layer of prismatic cells with thickened walls. (2) 

 A fibrous hypoderma consisting of four or five layers of polygonal 

 cells with thickened walls. (3) A layer of brown cells. (4) An 

 inner epidermis of very long, flattened cells. 



The seed is enveloped in three coats : (1) An outer coat com- 

 posed of cells with very sinuous walls. (2) A middle coat of cells 

 with lacunae. (3) An inner coat of elongated cells. 



Within these coats is an aleurone layer consisting of a single row 

 of cubical cells ; then the endosperm filled with starch. 



The grains of starch are simple, and either isolated or ag- 

 glomerated into masses. The isolated grains are bluntly or some- 

 times sharply angular, or often rounded. They may attain 

 10 or 12/x in diameter, but average abcut 4 to 6/x. They possess a 

 small distinct hilurn, and exhibit a tendency to agglomerate. 



Buckwheat starch always contains a number of abnormal grains 

 larger than the others ; they are irregularly enlarged, often bearing 

 some resemblance to an hour-glass. 



The diagnostic characters of buckwheat flour are : 



(a) The characteristic starch grains. 



(b) The epidermis of the seed-coat, the cells of which have very 

 sinuous walls. 



(c) The middle layer, the cells of which exhibit lacuna. 



