no 



THE MICROSCOPE. 



OAT was formerly much used as food for man, especially in 

 cool climates, where it is cultivated with the best success. 

 Its native country is not certainly known, though probably North- 

 ern Europe or Asia. There are several distinct species of oats, 

 the one generally cultivated in this country is avena sativa. Oat 

 flour does not form a dough or paste like wheat flour, so it 

 can never be used as a substitute, although it is frequently 

 mixed with wheat and sold under the name of wheat flour. 



Fig. J. Oat Starc/i. X 4/j. [Drawn with the camera lucida.) 



Oat flour, however, contains a large amount of nitrogenous mat- 

 ter. The grains or kernels of oat are usually found in market 

 inclosed in their husks. The first fruit coat of oat is com- 

 posed of several layers of cells. The cells of the first layer are 

 large, long and bordered with thin beaded walls: From the 

 cells of this outer layer of the first fruit coat, and from any 

 point on its surface, arise long epidermal hairs, always turn- 

 ing toward the apex of the grain, where they are much more 

 numerous. 



