Sept. 22, 1923 
A New Type of Orange-Rust on Blackberry 
493 
conditions would be right for hybridization. It was at first thought that 
such a type of infection had actually occurred in nature, thus accounting 
for the two kinds of sori in the three plants mentioned. The evidence, 
however, is against such a supposition. The writer has recently obtained 
a number of blackberries not only from Forestville, but from other 
localities, in which the rust w r as maturing two kinds of aecidia. The 
typical short-cycled rust has waxy, yellowish orange spores, but the 
short-cycled sori in plant No. 292, for example, are of an even darker and 
more reddish orange than are the long-cycled sori from the same leaves, 
and the spores also correspond in shape and size to spores of the typical 
long-cycled form. If we had two mycelia in the leaf the short-cycled 
Caeoma nitens type should be yellowish orange. The chances that teleuto- 
spores of the Gymnoconia and aecidiospores of the short-cycled form 
would mature at the same time in a given locality are rather remote. 
The writer has, however, collected good orange-rust aecidia in September. 
The seasonal conditions which would ordinarily bring out the orange- 
rust stage of one form would be just as favorable for the development of 
that stage of the other form. The time intervening between the sowing 
of the aecidiospores of the Gymnoconia and the development of its 
teleutospores is at least one month, and is usually much longer. Aside 
from the old doctrine of immutability of species, the best evidence that 
two mycelia are actually present in these leaves is the fact that the two 
types of aecidiospores are generally borne in separate sori. 
Several blackberries have been inoculated with aecidiospores from 
No. 292, 293 and 296. Teleutospores have already matured. We shall 
wait with interest until next spring to learn, in case there is systemic 
infection, whether or not the new rust will develop two sorts of aecidia. 
If it does it will have been proved that this phenomenal development of 
two kinds of aecidia is not due to the presence of two different orange- 
rust mycelia in the same leaf, but is due rather to the unstable nature 
of this particular form. 
The writer stated in a recent paper 4 that if one should visit Schweinitz’s 
old collecting ground at Salem, N. C., about May 15, he would probably 
find the long-cycled Gymnoconia on blackberry. The opportunity was 
afforded the writer himself to make this trip May 19,1923, and he had no 
difficulty in picking up any number of specimens of rust on blackberry 
which by color and test by spore germination were proved to be long 
cycled. Just which rust Schweinitz 5 had, however, when he described 
Caeoma nitens is far from a certainty. The Gymnoconia was also found 
to be very common at Cornelia, Ga., May 17. Teleutospores will be 
developed on blackberry here about August. 
The short-cycled rust on dewberry in more southern areas is a well- 
fixed form, morphologically distinct from the Gymnoconia on black 
raspberries and on Rubus saxatilis , of Europe and Asia. The fact 
that one form is maturing two kinds of aecidia, as described above, 
may indicate that a third type is arising. The aecidiospores are far 
more like those of the long-cycled Gyumoconia. The evidence based on 
distribution also favors the belief that the long-cycled orange-rust is the 
more primitive. Only this type occurs in Europe and Asia, and it is 
now known over most of North America, probably extending as far south 
and west as the short-cycled form. The westerly winds might well have 
* Dodge, B. O. op. cit. 
6 Schweinitz, Lewis David von. synopsis fungorum carolinaE supErioris . . . ed. a D. E. SchwaE- 
griciien. 105 p., 2 col. pi. 1822. E. Commentariis. Societates naturae curiosorium lipsiensis excerpta. 
