330 
Journal of Agricultural Research 
Vol. VIII, No. 9 
A glance at the table shows that practically any part of the host plant 
may contain internal sori. According to the accounts of different 
authors, sori were found buried deep in the tissue of the host plants, 
freeing their spores into hollow stems, or intercellular spaces, and in some 
cases making room for the lengthening spore chains by forcing aside the 
surrounding parenchyma cells (PI. 88, B ). Of course, the sori in 
seeds had little room to expand. Fromme (3, 4) has reported odd cases 
where the pycnium was located in the secium. The discovery of these 
internal sori has probably been accidental in all cases, although the 
investigators may have been looking for abnormal conditions. 
OBSERVATIONS ON THE INTERNAL TELIA OF CRONARTIUM RIBICOLA 
It will be noted that the fungus genera mentioned in Table I all 
belong to the Puccinia and Uromyces groups. So far as the writer is 
aware, there have been no reports of internal sori of any species of the 
genus Cronartium. In the course of intensive investigations on Cro¬ 
nartium ribicola Fisher, the white-pine blister rust, a striking case of 
the development of internal telia was discovered in the petiole of Ribes 
roezli (Regel) Coville and Britton. The plant was inoculated in July, 
1915, and was kept in the greenhouse through the following winter. On 
February 28, 1916, telia were found by Spaulding 1 on the petiole of one 
dead leaf and of one partially dead leaf, both still remaining on the 
plaiit. These petioles were killed, embedded in paraffin, and sectioned. 
Close to the base of the leaf the pith and pericycle regions (Pi. 88, A) 
of the petiole were found to be practically stuffed with the mycelium of 
the parasite, while farther from the leaf base there was less complete 
destruction of the host tissue. Haustoria, which were larger and more 
numerous than those in the leaf, suggested that the mycelium was more 
active in the petiole than in the leaf. At intervals in the tissue of the 
regions mentioned telia had begun to develop (PI. 88, E). The direc¬ 
tion of growth of what would normally be telial columns was very vari¬ 
able, some growing toward the outside, some toward the center of the 
petiole. Quite naturally the telia could not produce a typical telial 
column in such cramped quarters, and the variations were such as one 
would expect; the sori were broadened out (PI. 88, D), the spores com¬ 
pressed, and the columns where partially developed were coiled or bent 
by the pressure on the free ends (PI. 88, C). Despite the distortion of 
the columns, the spores quite closely resembled the spores from a normal 
sorus, lacking, however, in many cases, the heavier brown wall, char¬ 
acteristic of the fully developed spores of an external column. Possibly 
the walls would have taken on the brown color as the spores matured. 
In several of the sori, older than the others, the spores were just begin- 
1 Dr. Perley Spaulding, of the Office of Forest Pathology, supplied the material for this study, and kindly 
furnished the data on the inoculation. 
