924 
Journal of Agricultural Research 
Vol XXVIII, No. 9 
It was noticed that where leaves were left in damp chambers overnight, aecidi- 
ospores would be found dusted over areas considerably beyond the margin bear¬ 
ing sori as though the spores had been discharged from the aecidia with some 
force. In order to prove whether this was a fact, the following simple method 
was employed. Petri dishes about 2 cm. in depth, containing a small amount 
of agar to maintain the desired humidity, were prepared. Small squares of the 
leaf bearing aecidia were set up against the side of the dish (fig. 1, F.) in such 
a way that should the spores be discharged violently, they would be shot out 
and come to rest on the agar. Within a few minutes after the apparatus was 
set up, it was found that a number of spores had already been discharged, some 
of them coming to rest fully a centimeter and a half from the point of discharge. 
F 
Fig. 1 . —Aecidiospores of Puccinia podophylli Schw. (A), A chain of young spores showing the basal cell 
surmounted by three spores and a peridial cell. The first spore shows no local thickenings of the wall. 
The other two spores show two pore plugs. No plugs are developed in the walls of the peridial cells. 
(B) Four spores with one pore in each similarly located showing in this section. (0) Large spores 
with exceptionally large pore piugs. (D) Oblique section; four plugs in one spore. (E) Deep inden¬ 
tations in upper spore from pressure due to the development of the plugs and not to shrinkage in fix¬ 
ation. (F) Spore print of aecidiospores on agar. A small piece of leaf was fastened against the side 
of the Petri dish. As the spores were discharged they came to rest on the agar 
After 18 hours, a definite spore print had been laid down. The largest number of 
spores had come to rest somewhat over one-half a centimeter away from the 
aecidia discharging them. During a number of trials, it was found that very few 
spores were shot beyond a distance of cm. In order to find out how high 
the spores could be shot vertically, pieces of the leaves bearing aecidia were laid 
on the agar in the bottom of the dish so that spores shot upward would strike 
the cover. To insure that the spores would stick to the cover, a thin layer of 
agar was spread over its surface. Very few spores were found on the cover when 
it was placed 1 cm. above the leaf. 
Dr. A. H. R. Buller 4 has written the author that he believed a light object 
like an aecidiospore would be projected vertically just about as high as it would 
4 Tbe reader will find an interesting account of experiments with the “toy balloon-gun” illustrating 
spore discharge in the following book: Buller, A. H. R. Researches on fungi. 2: 33-38. New 
York. etc. 1922. 
