G2 



I. POLYGONAL GRAINS. 



A Corn (Maize). 



L Size. Grains usually 15— 25^ in diameter. (Very few 

 smaller.) 



2. Form. Sphaero-polygonal or sharply polygonal. 



a. Compact aggregates not present. 



3. Laminae (rings). Not visible. 



4. Hilum. Central, — very distinct. 



a. Often with radiating clefts. 



5. Polarization Crosses. Brilliant, distinct crosses. 



6. Selenite Plate. Indifferent play of colors. 



B BUCKWHEAT. 



1. Size. Grains usually 5 — 12/x in diameter. 



2. Form. Sharply polygonal or sphaero-polygonal, more 



often. 



a. Angular aggregates or rod-like aggre- 

 gates usually present. 



3. Laminae. Not visible. 



4. Hilum. Very distinct. 



5. Polarization Crosses. Distinct. 



6. Selenite Plate. Indifferent play of colors. 



C OATS. 



1. Size. Grains usually 5 — S^u in diameter. (Very seldom 



larger) . 



2. Form. Well defined polygons. 



a. Spindle-shaped single grains also occur. 



(Characteristic of oat starch.) 



b. Rounded aggregates often occur. 



3. Laminae. Not visible. 



4. Hilum. Absent. 



5. Polarization Crosses. Distinct. 



6. Selenite Plate. Indifferent play of colors. 



D RICE. 



\. Size. Grains commonly 2 — lix in diameter. (Rarely 

 larger) . 



