130 
IOWA ACADEMY OF SCIENCE Voi. XXVII, 1920 
Fig. 26. Machine to determine the force necessary to puncture the pericarp of 
sweet corn. 
glass tube was inserted into a cork and it in turn was securely 
placed in a vial supported by a clamp attached to a support. 
By such an arrangement it became an easy matter to centralize 
the pressure exerted by the glass needle. Weights were then 
added until the pericarp layer was punctured. The pans used 
plus the friction of the attached corn represented a weight of 
32 grams. 
The variety of sweet corn used was the well known Stowell’s 
Evergreen. The corn came originally from Connecticut but had 
been grown in Iowa for varying periods, one, two and three 
years. The corn was carefully selected from the plots so that 
the three stages, canning, dented and mature were typical for 
such designation. The number of grams necessary to cause pen- 
etration of the first series, that which has been grown in Iowa 
