June 7,1924 
Uninucleated Aecidiospores in Caeoma Nitens 
1047 
OCCURRENCE OF CAEOMA NITENS WITHOUT SPERMOGONIA 
Miss Ruth Colvin, who was assisting the writer with this work, made one 
collection of orange-rust about every mile from wild blackberries May 24 along 
the road between Washington and Fairfax, Va. The results of her germination 
tests show that only 11 of the 30 collections were of the strain whose spores 
develop 2-celled promycelia; only one long-cycled specimen was obtained, in 
this case the host happened to be the black raspberry, Rubus occidentalis. In 
most regions around Washington one would certainly find on such a trip black¬ 
berries infected with the long-cycled form. 
Miscellaneous gatherings on wild blackberries near Upper Marlboro, Md., 
always contain some specimens which are long-cycled. Twenty-two specimens 
were gathered from wild blackberries in this region June 2. The presence or 
absence of spermogonia was determined in the field by Prof. R. A. Harper and 
Dr. C. L. Shear. Of the 22 gatherings, seven happened to be long-cycled; the 
spores from the eight specimens without spermogonia produced 2-celled promy¬ 
celia, and those from three gatherings developed only 4-celled promycelia. 
The rust on three different plants was of the type which develops spores of two 
sorts; some produce long germ tubes characteristic of the long-cycled forms, 
others germinate with 4-celled promycelia. The specimens which were proved 
to be of the long-cycled type were also characterized by the greater abundance 
of spermogonia. 
The results of germination test of specimens collected May 9 at Chadbourn, 
N. C., and May 10 to 12 at Louisville and Vidalia, Ga., are such as to suggest 
that the strain which does not develop spermogonia normally and whose spores 
form 2-celled promycelia, greatly predominates in the South. The specimens 
tested, however, were gathered within a limited area in each place, so that a 
further survey would be necessary in order to determine this point. Of the 
18 specimens tested only one was found which developed 4-celled promycelia. 
This was found on Rubus trivialis at Louisville, Ga. 
Miss Colvin sent in 11 specimens gathered May 30, between Washington, D. C., 
and Gettysburg, Pa. No spermogonia could be found on leaves of six specimens 
whose spores developed 2-celled promycelia. Spermogonia were abundant on 
four different specimens, three of which were short-cycled and formed 4-celled 
promycelia. The other one was long-cycled. One specimen showed a few sper¬ 
mogonia and some 4-celled promycelia were found in the culture but 2-celled 
promycelia were much more abundant. A few other cases of infection found 
elsewhere have proved to be of a type where 2-celled promycelia are developed, 
although spermogonia are present on the leaves. 
On June 3, 19 collections were obtained at the experimental farm at Bell, Md. 
Leaves on nine infected plants showed spermogonia and the rust was of the 
4-celled promycelium type in six cases; the other three gatherings were long- 
cycled. Spores from nine specimens showing no spermogonia developed 2-celled 
promycelia. One large plant with a number of canes was clearly infected with 
two different strains of orange-rust. Leaves on most of the canes showed an 
abundance of spermogonia. Here the rust was long-cycled. No spermogonia 
could be found on leaves on one cane and here the rust was short-cycled, the 
promycelia being 2-celled (see PI. 1, B, D). 
On June 12, Professor Harper and Dr. F. D. Fromme sent in nine specimens 
from rusted blackberries gathered on the road to Mountain Lake, Va. No sper¬ 
mogonia could be found on the three specimens whose spores germinated with 
2-celled promycelia. Five specimens showed an abundance of spermogonia. 
Only one of this number proved to be short-cycled, 4-celled promycelia being 
formed as the spores germinated. 
96461—24t-6 , J 
