191i] PRITCHARD—DISSEMINATION OF PUCCINIA 187 
or embryo. As many as to pustules are sometimes seen in a 
single section, and nearly all of them are wholly inclosed by the 
tissues. All about the pustules are masses of rust mycelium, but 
the hyphae are not confined to these areas. They extend con- 
siderable distances from the pustules, and are present in numerous 
grains in which teleutospores cannot be found. 
To obtain further information relative to infection through 
the seed, badly rusted grains of wheat after germinating from 
one day to two weeks were studied in the botanical laboratory at 
Madison, Wis., by means of cytological methods. The seed avail- 
able was a remnant of former experiments, 4 or 5 years old, and 
revealed some very interesting phenomena. 
Teleutospores in certain pustules, lying in the region of the 
hilum, were found to be undergoing remarkable changes, resembling 
the so-called palmella formations of certain filamentous algae. 
The protoplasts appeared to grow and divide in various directions, 
often distending the walls until they became quite thin (figs. 5-13). 
The nuclei, though not well fixed, were present as irregular densely 
stained bodies. Frequently one or both cells of the teleutospore 
were still undivided (figs. 1-3, 15), but numerous later stages were 
present, in which the protoplast had divided one to several times. 
As a rule, the wall between the two original cells was quite thin and 
persisted for some time (figs. 5, 6, 8), but occasionally it could not 
be distinguished (fig. 7).. In the latest stages observed the cells 
became more distinct, often rounding slightly and acquiring 
thicker walls (figs. 7, 8, 11, 12). A view of the apical end of the 
teleutospore represented by fig. 12 is shown in a lower focus in 
fig. tr. In numerous cases the two halves of the former teleuto- 
spore finally separated from each other, forming two more or less 
globular multicellular aggregates (figs. 13@, 18). That these 
conditions are due to a parasitic mycelium, which has penetrated 
the teleutospores and completely replaced the protoplasts of the 
rust, is of course a possibility to be reckoned with. As is seen 
from the figures, however, direct evidence of the presence of such a 
parasite is entirely lacking. There is no mycelium outside the 
rust cells, and no evidence of a gradual absorption and replace- 
ment of the rust protoplast by that of a parasite. The subsequent 
