258 BOTANICAL GAZETTE [OCTOBER 
This was pressed down and around the stem by tightening the bolts 
which were used to draw the two blocks together. This method was 
satisfactory. It was soon found, however, that the stem could be 
held sufficiently firm by substituting moist cotton for the mixture of 
sand and Portland cement. Moist cotton, therefore, was used in all 
the experiments as packing to fasten the stem in the blocks. 
When the stems were fastened in the blocks, one pair of blocks 
was hooked to the spring balance, and the other pair was secured 
to one end of the wooden frame. The spring balance was hooked 
in turn to an iron rod passing through the opposite upright of the 
wooden frame. On the end of this rod, protruding beyond the frame, 
was a large tail-nut. By turning this tail-nut with the hand, tension 
was brought on the spring balance, and through the balance on 
the plant stem. The breaking strength was read from the face of 
the spring balance. 
: After the stems were broken they were preserved either in 50 per 
cent. alcohol, or short sections were cut from just below the breaking 
point in the stems, and these were killed and fixed in 1 per cent. chrom- 
acetic acid, thoroughly washed, dehydrated in alcohol, and kept for 
future study. 
The following methods were used in making microscopic examina- 
tions and measurements of the xylem and hard bast in the stems. 2 
Method 2.—Measurements of the thickness of cell walls in sae 
free-hand sections, and also in some cases of microtome sections, 
were made by using an ocular micrometer. The results record 
are in each case an average of eight measurements taken in as many 
distinct areas of the cross-section. oa 
Method 3.—The total xylem and hard bast areas were meast : 
in some of the experiments by projecting a cross-section of the 
upon a bristol-board screen, and measuring the areas with a po 
planimeter. . fe 
Method 4.—Camera lucida drawings of the total xylem an i 
bast areas and also of the hard bast elements were made upon oe 
ardized bristol-board. The drawings were very carefuly cut ‘ 
with a sharp and pointed scalpel, and then weighed on @ ir ~ 
balance. The number of hard bast elements were also count ae 
fastening the drawings of the hard bast elements over sheets of y 
Le Ay Rae een ea ee 
