32 FLOUKS. 



(23) Oat Flour. 



The oat grain is also enclosed between two palese which may 

 furnish valuable means of identifying the flour. The grain may 

 also be distinguished from the three foregoing grains by the follow- 

 ing characters : (1) By the elongated shape of the hairs which are 

 also often geminate. (2) By the cells of the outer epidermis of the 

 pericarp, which have very thin walls and fairly numerous pits. (3) By 

 the irregular polygonal shape of the cells of the hypoderma, of which, 

 however, there is but little to be found. (4) By the cells of the seed 

 coat, of which there is only a single row ; they are polygonal or fusi- 

 form in shape, pale yellowish-brown in colour ; their walls are 

 smooth and seldom pitted, and the cells often exhibit an irregular 

 arrangement. (5) By the starc'i which consists of small simple 

 rounded grains associated with a number of large oval compound 

 grains and the isolated angular constituent grains of the latter. 



