124 
IOWA ACADEMY OF SCIENCE Vor,. XXVII, 1920 
vigorously growing volunteer corn which was collected when in 
flower, October 8th, three days before a killing frost. The fourth 
to the seventh internodes were selected, split lengthwise, and 
cut to a length at which they would weigh ten grams. These were 
dried, and lost about 90 per cent of their weight. The dry tissue 
was stored in the laboratory until used. 
The colloidal mixtures were made up according to the general 
method for making media. One and five-tenths grams of egg 
albumen were added to nine hundred cc. of agar after cooling to 
40° C. These media were poured on porcelain plates which had 
been greased with just enough vaseline to show a “grain” when 
rubbed with the finger. Two hundred cc. were used in each 
case. After the prepared colloidal material was poured into the 
plates, it was allowed to remain in the laboratory for some time. 
Drying was hastened by blowing air over the plates by means of 
an electric fan. The colloids were later cut into pieces of the 
desired size, 30 square mm. Further drying was resorted to by 
placing the preparations in an electric oven held at 70° C. The 
squares after being trimmed off by means of a sharp pair of 
scissors were allowed to come to an equilibrium with the air 
before being used. The average thickness of the dry pieces 
was 0.145 mm. Throughout the work three solutions were used, 
namely, distilled water, 1/100 N solution of citric acid and 
1/100 N solution of sodium hydroxide. The experiment was 
carried on at room temperature which was about 24° C. 
The colloids were placed in a 7 cm. petri dish without cover 
which was placed in a 10 cm. petri dish. These were kept in the 
laboratory locker from which they were taken for weighing. 
The corn tissue was weighed and put in 100 cc. wide mouthed 
bottles. Four sections of each colloid and corn tissue were treated 
with distilled water, sodium hydroxide and citric acid. 
The increase in absorption was ascertained by weighing. The 
weights were taken over a period of 39 days for agar and agar 
with egg albumen in the acid and sodium hydroxide solutions; 
81 days in water was needed to bring the corn stalk tissue to 
its absorption maximum. The weighings were however, con- 
tinued until there was a distinct loss in weight or the pieces 
began to break up so that accuracy could no longer be secured. 
For the first week the extent of absorption was determined daily 
but after that weighings were made once a week since excessive 
handling was not desirable. Before being weighed each piece or 
section was carefully dried between sheets of filter paper. 
