EXPLANATION OF THE ILLUSTRATION 
Prare XXVIIL. Type archaeological specimens for 
the various grades of induration which were used 
to estimate teosinte introgression, A, grade-1; B, 
grade-2; C, grade-3; D, grade-4 long cob; BK, 
grade-4 short cob; F, grade-5. The most 'Tripsa- 
coid specimen (F) has a few single spikelets. Nat- 
ural size. 
