SCHREINER & SKINNER: EFFECT OF GUANIDIN ON PLANTS 539 
Perforated aluminum disks were floated, by means of a raft 
prepared from sealed glass tubing, in such a way that the disks 
were kept just at the surface of the water when loaded with seeds. 
The wheat seeds, previously soaked in water, for about two 
hours, not longer, were spread evenly on the surface of the disks. 
The perforations in the 1.6 mm. thick aluminum were approxi- 
mately 3.2 mm. in diameter and 2mm. apart. The entire arrange- 
ment of raft and disks was floated in a porcelain-lined iron tank. 
The seedlings were used when the plumule was about 2 cm. high 
and just ready to emerge from the enveloping sheath. In this 
manner the 1,320 uniform seedlings required for each experiment 
were readily obtainable. 
The bottles used in these cultures were made of flint glass 
and were stoppered by means of a soft flat cork about 12 mm. in 
thickness and notched for holding the seedlings. The method of 
notching these corks consisted in cutting 10 vertical, triangular 
wedges from the circumference of each. Each wedge after being 
cut out was truncated, so that when it was replaced, a small 
triangular opening was left through which the plumule of the seed- 
ling passed. This hole was large enough to hold the seedling 
firmly and yet not bruise or injure it in any way by pressure. 
Around the circumference of the cork, in the upper half, a groove 
had been made sufficiently large to hold a small rubber band. 
After the wedges were inserted, the band kept them in place 
and allowed the cork with the seedlings to be handled readily 
and put into or taken out of the bottle without disturbing the 
plants. 
As already mentioned, these solutions were changed every 
three days. This was done by putting up other triangles of bottles 
Similar in every respect to the ones just described. The corks 
With the plants were then transferred from the old solution to the 
Corresponding new solution. 
EFFECT OF GUANIDIN ON WHEAT 
As already mentioned, two sets of the cultures were prepared ; 
One was used as a control; to the other was added guanidin car- 
bonate, 25 parts per million to each culture. The wheat seed- 
lings grew from February 15 to February 27, I9II, the solutions 
being changed every three days. 
