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GRABE, D.F. (ed.) 1970. Tetrazolium Testing Handbook for Agricultural Seeds. Contribution No. 29 
       to the Handbook on Seed Testing,  AOSA.  Figure 9 Crimson Clover.
originally appeared  in:  Delouche, J.C., T. W. Still, M. Raspet, and M. Lienhard. 1962.  The tetrazolium test for seed viability.
        Miss. Agric. Exp. Sta. Tech. Bull. 51.
  Figure 9.  Criteria for interpreting tetrazolium test results on crimson clover seed.  Illustrations are paired and depict both sides of the seed.  Black areas indicate stained, living tissue;  white areas represent unstained and dead tissue.
1.     Germinable.  Seed completely stained.
2-4.  Germinable.  Minor unstained areas on cotyledons.
5.     Germinable.  Minor unstained area on upper portion of radicle-hypocotyl axis.
6.     Germinable.  Extreme tip of radicle unstained; minor unstained spots on cotyledons.
7.     Non-germinable.  More than extreme tip of radicle unstained.
8.     Non-germinable.  Unstained area at juncture of cotyledons and radicle-hypocotyl axis.
9.     Non-germinable.  Unstained area near point of attachment of cotyledons and radicle-hypocotyl axis over where plumule develops. 
10.   Non-germinable.  Radicle-hypocotyl axis bisected by unstained area.
11.   Non-germinable.  Unstained areas on radicle-hypocotyl axis and at point of attachment of cotyledons to axis. 
12.   Non-germinable.  More than one-half of cotyledonary tissue unstained.
13.   Non-germinable.  Radicle-hypocotyl axis unstained.
14.   Non-germinable.  Seed stained off-color, grayish red, orange red or glassy or transparent red color.
15.   Non-germinable.  Seed completely unstained.