1899] THE CEREAL RUST PROBLEM 343 
cotton-wool was loosely twisted round the base of each of three plants, 
extending up the plant about half an inch from the muslin on which 
the plants were growing. Three circles of stout white sterilised 
blotting-paper, each with a small hole in the centre and a slit from the 
hole to the margin, were prepared. One of these blotting-paper collars 
was placed round the stem of each of the wheat plantlets already 
enveloped at the base with cotton-wool, on which the blotting-paper 
rested, and was kept moist by the water conducted by the wool. 
Fresh uredo-spores of Puccinia glumarum were deposited in abundance, 
by means of a scalpel, on the damp blotting-paper at a distance of 
about one line from the stem of one of the plants; at a distance of 
about three lines from the stem in the second example, and in a circle 
about four lines from the stem in the third experiment. 
Within a week of depositing the spores on the blotting-paper, the 
plant to which the spores were placed nearest drooped and fell over as 
in the disease known popularly as “damping off.” Microscopic 
examination showed that death was due to a dense weft of mycelium 
emanating from the germinating uredo-spores that had surrounded the 
stem of the plant. I could not, however, demonstrate satisfactorily 
that any of the hyphae had penetrated the tissues of the wheat 
plant. 
Within eighteen and twenty-two days respectively from the date of 
placing the spores on the blotting-paper, the two remaining plants 
showed uredo-pustules on the upper surface of the lowest leaf; in both 
instances the pustules appeared at a point about one inch above the 
blotting-paper. This, however, I do not hold to prove that the 
mycelium travelled upwards for that distance in the tissues of the leaf, 
but rather consider that the leaf increased an inch in length between 
the period of inoculation and the time the pustules first became visible 
externally. The remaining plants not inoculated remained free from 
disease. 
The above experiment proves satisfactorily, I think, one point, 
namely, that it is not necessary that the uredo-spore should be in 
actual contact with the host-plant to insure inoculation, but that the 
germ-tube can live for some time as a saprophyte, when, if conditions 
are favourable, it can enter the tissues of a host-plant and assume 
parasitic functions. This feature may prove to be of great importance 
from the practical point of view in combating the disease. During 
the present season I hope to conduct further experiments for the pur- 
pose of ascertaining for how long a period the mycelium can grow as a 
saprophyte without losing its power of inoculating a host-plant, and 
also what distance it can traverse before effecting the same. 
During the present spring an experiment was conducted on similar 
lines to the above, only teleutospores were used instead of uredo- 
spores. In this instance only one out of three infected plants pro- 
duced uredo pustules, whereas an uninfected or check plant also showed 
