Mar. 15, 1924 
Currant Cane Blight Fungus on Other Hosts 
841 
currants in the near neighborhood, from which the fungus might easily 
have spread to the roses. 
The symptoms produced by the currant cane blight pathogene on the 
rose differ somewhat from those on the currant. In some cases the entire 
cane is not blighted and the lesions remain as definite cankers on the 
stems (PI. 1 A, B, E). The small pimple-like fruiting bodies of the fun¬ 
gus are distributed over the surface of the cankered bark which is of a 
characteristic “seal brown’ ’ 8 color. The region surrounding the lesions is 
often “vinaceous brown” shading to “dark Corinthian purple” next to 
the edge of the canker. Recently blighted canes, upon the development 
of the fruiting structures of the fungus, become speckled with slightly 
raised golden brown dots (PI. 1, C). As the fungus develops, consider¬ 
able areas may present this golden brown color which, with the natural 
sheen of the bark, makes the cane appear as though gilded. These sur¬ 
faces later become dull, owing to the further development of the dark 
stromata beneath. In some cases the two shades of brown are arranged 
more or less concentrically as shown in Plate 1, D. The diseased canes 
may become so swollen that the bark is roughened and split longitudinally 
(PI. 1, E). 
The manner in which the pathogene gains entrance to the rose is not 
known but it seems very likely that infection usually occurs through a 
bud or young shoot from which it passes to the main stem (PI. 1, A 
and B). Small lesions have been observed, however, where no buds, 
shoots, or visible abrasions were present. As in the currant, the fungus 
evidently penetrates all parts of the stem, having been isolated from both 
the cortex and wood in which the mycelium occurs intercellularly. 
IDENTITY OF THE FUNGI FROM THE THREE HOSTS 
Until the autumn of 1923, comparisons of the chromogenic fungi from 
horse-chestnut, rose, and currant were based on cultural characters, 
pycnospore size and their parasitism on currant. During July of that 
year, however, ascospores developed on the inoculated rose plants, and in 
September and October mature ascospores were found on the currants 
which had been inoculated with the fungus from rose and from horse- 
chestnut, respectively. A careful comparison of the material from the 
various hosts was now possible. 
In Grossenbacher and Duggar’s description of the currant cane blight 
fungus, the stromata are described as being 1-4 mm. in diameter, usually 
2-3 mm. The perithecia measured 175-250/1 in width. The asci were 
80-120 jx by 17-20 n and the ascospores 16-23/4 by 5-7/4* They describe 
the pycnidia as having about the same size as the perithecia, and the 
pycnospores as measuring 16-31/4 by 4.5-8/4. 
The perithecia of the fungus which developed on currant and rose 
from inoculations made with material from the various hosts were of 
practically the same size and agreed closely with those of the parasite 
which had developed from natural infections, although because of the 
relation of the perithecial wall to the surrounding tissues of the fungus, 
it is difficult to make accurate comparative measurements. 
Measurements of over 200 ascospores of the currant cane blight fungus 
from various localities gave a range in size from 14-27/4 by 5-10/4, though 
8 Ridgway, R. 
1912. 
color standards and color nomenclature. 43 p., illus. Washington, D. C* 
