[Vor. 4 
104 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
same radial line as was used to determine the percentage of 
summer wood. The distance of the culture block from the 
pith was taken as the distance in inches from the center of the 
culture block to the pith. If the sample did not contain the 
pith the location of the latter was determined from the aver- 
age curvature of the annual rings. 
One resin analysis was made for each column of culture 
blocks, a block of an average specific gravity for the column 
being used. The samples to be analyzed for resin were kiln- 
dried at 65° C. until they reached constant weight. They 
were then removed to a desiccator to cool to room tempera- 
ture, after which they were planed into fine shavings, which 
were stored in stoppered bottles until used. Five-gram quan- 
tities of shavings were used for each analysis. The shavings 
were placed in the upper chamber of a Soxhlet extraction 
apparatus which contained enough glass wool to prevent 
them from siphoning off when the chamber was emptied auto- 
matically. The solvent for extraction was benzol, and the 
extraction was continued for 36 hours for each sample. Small 
Westinghouse electric dise stoves of 1.8 amperage were used 
to keep a constant heat. After extraction the benzol contain- 
ing the resin was distilled, and the resin transferred to a 
tared watch-glass, and the contents dried to constant weight 
in an electric oven kept at 60-65° C. The resin percentages 
given in table 1 are based on the total hard resin thus ex- 
tracted and dried. 
PREPARATION OF CULTURES 
For cultures wide-mouthed jars of one quart capacity were 
used. In the bottom of each jar there was placed a 3-inch 
layer of macerated paper, the well-known Scott’s toweling 
being employed for this purpose. This paper had previously 
been soaked in distilled water for several hours to remove all 
readily soluble chemical compounds. After this it was 
squeezed out, then again rinsed in distilled water, and finally 
squeezed out until fairly dry before being placed in the jars. 
Upon this layer the blocks were placed on end, as can be seen 
in plate 9. The jars were plugged with cotton and sterilized. 
