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IOWA ACADEMY OF SCIENCE VoL. XXVII, 1920 
Fig. 25. Graph showing the progress of absorption occurring in corn stalk tissue 
and in colloidal mixtures. 
experimental error. The greatest change in absorption is caused 
by the addition of albumen to agar, when immersed in citric 
acid, which for the first day is the same as plain agar in citric 
acid. 
Discussion . — Direct comparison of percentages with other in- 
vestigators cannot be definitely made because there is such a 
variation in the conditions under which the work was done. The 
results as far as their physical nature is concerned, are much 
the same. 
MacDougal has found that in Opuntia young tissue absorbs 
least; mature, most; and old, between the two extremes. We 
considered this corn tissue to be young and it is likely that mature 
plants would show a much greater amount of swelling. This 
might bring the maximum swelling more nearly up to that of 
agar in acid or alkaline solution. MacDougal has been able to 
greatly reduce the absorption of water and bring it more nearly 
