ZEA 175 



it is flattened in a plane at right angles to the length of the 

 cob. The broader surface is roughly triangular in outline, 

 being broader above than at the base. The groove indicates 

 the position of the embrvn At the " tip " of a mature grain, 

 may still be found the papery remai ns ("chaff") of the pal et, 

 lemma, andglumes of the pistilla te sp ikelets. The point of 

 the grain, where it was attached to the cob, is the peduncle 

 of the flower. The opposite indented end of the grain is 

 often marked by a small point which is the remnant of the 

 style. A longitudinal section of the corn grain parallel with 

 the broad surface will show, with magnification, the follow- 

 ing parts. 



1. Pericarp, of several layers. 



2. Testa, inner integument, of two layers. 



3. Nucellar tissue. 



4. Aleurone layer, outermost layer of endosperm, a single 

 row of cells. 



5. Starchy endosperm. 



6. Horny endosperm. 



7. Embryo. 



8. Tip cap. 



The pericarp and testa form the hull. It is possible to 

 separate mechanically the starchy endosperm into two parts, 

 the crown starch and tip starch. 



The following is a fair average of the relative proportions 

 of the divisions of the grain, as given by Hopkins, Smith, 

 and East: 



Per cent. 



Embryo 1 1 . o 



Tip cap i.S 



"HuU" 6.0 



Aleurone layer 8.0 to 14.0 



Horny endosperm 43.0 



Starchy endosperm 25.0 



