492 
Journal of Agricultural Research 
Vcl. XXV, No. II 
producing two sorts of aecidia. Spores will germinate normally if 
floated on water or placed in hanging drops, but agar plates are far 
more convenient and satisfactory for this work. The writer’s method 
now consists in placing a leaf bearing young aecidia on agar in Petri 
dishes so that spores from individual sori fall together on the surface 
of the agar as they are naturally shed. A spore print is obtained in a 
few hours, showing the location of the ruptured sori on the leaf. The 
same leaf can be used several times to obtain additional spore prints 
for study. The strongly negatively heliotropic reaction which sends the 
germ tubes down into the agar will be avoided if the plates are more 
equally illuminated from below and above. The temperature factor 
need not be considered in this connection so long as the spores germinate. 
A SHORT-CYCLED RUST IN THE MAKING? 
As soon as spore prints of individual sori on leaves from plants No. 
292, 293, and 296 had been obtained, it was clear that the spores from 
all sori had not been discharged in the same way. Certain aecidia had 
shed spores that were very dry or powdery, so that they had been evenly 
scattered like dust on the agar. The spores from other aecidia seemed 
to be more waxy and tended to cling together, falling in little clumps, 
like waxy pollen. The dusty spores were shed from the sorus as soon 
as mature; the waxy spores tended to stay in the sorus and pile up in 
irregular masses. It was found that the spores in the waxy sori pro¬ 
duced promycelia, while the more dusty spores produced only long 
germ tubes. Contrary to what one would expect, the waxy sori (short 
cycled) were of a more reddish orange, while the others (long cycled) 
were more of a golden orange. The color contrasts showed very dis¬ 
tinctly in the spore prints. Considering, then, the waxy nature and the 
color of the spores, it was not at all difficult to tell by examining a sorus 
with a hand lens how its spores would germinate. 
DISTRIBUTION OF AECIDIA ON THE LEAVES 
The leaves on these blackberries have three leaflets. Sometimes all 
aecidia on the three leaflets will be long cycled, while those on another 
leaf will be short cycled. Again, all sori on the terminal leaflet will be 
short cycled, while those on the other two are long cycled. It was fre¬ 
quently noted that aecidia at the base of a leaf or leaflet were long 
cycled and those toward the tips short cycled, but no general rule seems 
to be followed in this distribution. Occasionally, a long aecidium was 
found in which the spores at one end were long cycled and those at the 
other were short cycled. This might have been caused by the running 
together of separate sori. The writer has had in mind the task of infect¬ 
ing the same blackberry systemically with both the long-cycled and the 
short-cycled forms of orange rust. Such an experiment would probably 
necessitate the development of teleutospores of the Gymnoconia in the 
greenhouse so that they could be sowed on new shoots of the blackberry 
at the same time that the aecidiospores of the short-cycled rust were 
being matured in nature. This would mean that the greenhouse work 
should begin about six weeks before the orange-rust appears in the field. 
Local gametophytic infections could be affected so that the mycelium 
of each type would remain isolated in different nodes, to run together at 
some common node. Should the two mycelia come together in a leaf, 
