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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 10 Cotton.
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 10.  Criteria for interpreting tetrazolium test results on cotton 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; stain not overly intense.
2-5.  Germinable.  Minor unstained areas on cotyledons.
6.   Germinable.  Less than one-third of cotyledons unstained.
7.   Germinable.  Extreme tip of radicle unstained;  minor unstained spots on cotyledons. 
8.   Non-germinable. More than one-third of cotyledons unstained;  extreme tip of radicle unstained.
9-10.  Non-germinable.  More than extreme tip of radicle unstained.
11.  Non-germinable. Unstained area on cotyledons extends into region where radicle and cotyledons are attached. 
12.  Non-germinable.  More than one-third of cotyledonary tissue unstained.
13.  Non-germinable.  Seed stained grayish-red, cloudy or milky red color;  cotyledons not expanded; seed relatively smaller than germinable seed.
14.  Non-germinable.  Seed stained abnormally dark; purplish red; cotyledons not expanded; seed relatively smaller than germinable seed.
15.  Non-germinable.  Seed completely unstained.