1 88 Bailey. — Puccinia malvacearnm and the Mycoplasm Theory . 
(2) by taking steps to exclude the entry of Collembolae, &c. 
With these objects in view the globes were fitted with large cork bungs 
replacing the cotton wads in the upper apertures. Each cork was bored to 
receive three tubes. In the centre a short wide tube, ordinarily plugged 
with cotton-wool, but available for the passage of any instruments, &c., 
necessary for inoculating or for withdrawing single leaves for examination ; 
on one side of the central tube a small inlet-tube, penetrating only a little 
way into the globe and with its exterior end passing into a wide tube, 
plugged with cotton, to act as a filter. The third tube was the one used 
for withdrawing the air : this one was bent to follow roughly the inside 
curve of the globe, and had its internal opening close to the bottom of the 
globe ; the external portion of this tube passed into a cotton-plugged tube, 
designed to act as a germ-filter in case the aspirator should fail. 
To the other end of this germ-filter was attached a tube which ran 
down into a small gas-jar and dipped below the surface of some water con- 
tained in the jar. A cork was inserted in the top of the gas-jar, and 
through this another short tube was connected by pressure tubing to a long 
gas-pipe, which passed in front of all the globes, and was, in turn, connected 
to an aspirator, which thus served to draw a continuous current of air 
through all the globes. The rate of the air current was equalized in each 
globe by watching the rate at which the air bubbled through the water in 
the gas-jars, and adjusting a pressure-clip, placed on one of the rubber 
connexions, so as to make the ‘ bubble rate ’ the same in each case. 
Owing to the shape of the upper neck of the globes, it was found 
difficult to get a ‘spore-tight ’ fit with the bung alone, and, to ensure this, it 
was found to be necessary to stretch a piece of rubber tissue tightly over 
the cork in each case before pushing it in. 
The general appearance of these globes, when in action, is shown in 
Fig. 2. 
In order, if possible, to exclude Collembolae, the earth used in this 
experiment was sterilized before starting, and, in addition, a layer of 
sterilized sand, one inch deep, was spread over the entire surface of the soil ! 
immediately before planting the seed. 
Finally a piece of fine muslin was tied over the bottom of the pot to • 
protect the drainage hole. 
The soil sterilization was carried out as follows : 
The soil was thrown into a large metal bin and sprinkled during the 
process with toluene ; cloths were then put on top and weighted down, and 
the bin was covered and left for 20 hours. At the end of that time the soil 
was tipped out on a clean cement floor, and stirred over four times in the 
two succeeding days. 
It was then put straight into the pots, which, together with the crocks, 
had been sterilized previously in a strong solution of formalin. 
