132 
IOWA ACADEMY OF SCIENCE Vor.. XXVII, 1920 
TABLE III. DATA SHOWING THE NUMBER OP GRAMS NEC- 
ESSARY TO penetrate the pericarp of ^^STOWEIUS EV- 
ERGREEN^' SWEET CORN WHEN DRY AND WHEN SOAKED 
FOR VARYING PERIODS. THE CORN HAD BEEN GROWN IN 
IOWA FOR SEVERAL YEARS 
Dry 
8Hrs. 
12 Hrs. 
24 Hrs. 
36 Hrs. 
48 Hrs. 
72 Hrs, 
Canning stage.. 
116.7 
75 
89.25 
73.5 
64.7 
72.7 
■ 63.2 
Dented.. 
119.S 
83 
92.75 
94.2 
71.8 
S7.4 
58.5 
Mature................ 
147.S 
74 
82.75 
99.2 
58.7 
80.2 
65.8 
kernels for different periods gives results that are at variance 
with each other. 
Considering the dry pericarp itself it is evident that there is 
much variation throughout. Knowing that plant tissues are 
modified considerably by the environmental conditions which 
affect the plant, it is only natural to expect variations in the 
three sets. The weather conditions of 1918 and 1919 were much 
different, the former being characterized by periods of very 
intense evaporation. The present study does not concern itself 
with the evaporating power of the air and its effect upon the 
balance between the forces of transpiration and absorption. The 
province of this publication is simply to show how the proposed 
mechanical device can serve as a measure of the toughness or 
mechanical resistance of the pericarp layer. 
Recognizing the fact that the data herewith submitted are 
meager yet the following conclusions are fully substantiated: 
(1) There is a considerable variation in the force necessary 
to penetrate the pericarp of sweet corn in the canning, dented 
and mature states : — the more mature requires the greater force. 
(2) Soaking sweet corn seed for varying periods from 8, to 
72 hours does not give a commensurate reduction in the force 
necessary to penetrate the pericarp. 
Department oe Botany, 
Iowa State College. 
