May 10,1924 Botryosphaeria and Physalospora on Currant and Apple 595 
The chief difference in the fungi, according to Putterill, lies in the fact that the 
asci of his form from apple are narrower than those measured by Grossenbacher 
and Duggar and the stromata of the apple fungus are usually about 0.5 mm. wide 
as contrasted with 2 mm. as the most common size on apple. Neither of these 
characters appears to the present writers to have significance. The asci are 
variable in width and are frequently found in material from currant no wider 
than those noted by Putterill. The stromata of this fungus, as already pointed 
out, vary in size with the thickness of the bark in which they grow. Mature 
perithecial stromata of B. ribis on rose are often 0.3 mm. or less in diameter, yet 
this fungus has been proven by inoculation experiments to be the same as that 
producing much larger stromata on currant. 
That the character of the bark in which they are produced directly influences 
the size of the stromata in this species seems to be fully proven by their artificial 
culture on sterile twigs from different species of woody plants. Plate 1, A and £, 
show mature pycnidial stromata which developed on dormant apple and currant 
twigs from subcultures of B. ribis from currant. These cultures were started at 
the same time and kept near together in special culture flasks on a bench in a 
greenhouse from November 19, 1921, to February 22, 1922. A glance at the 
figures will show the relative size of the stromata on the two hosts. To be sure 
these are pycnidial stromata as the writers are not yet able to produce mature 
perithecia in quantity in pure culture. Under natural conditions, however, 
perithecia are often produced in the same stromata with pycnidia and on any 
given host the stromata bearing the two kinds of spores are of the same size. 
Unfortunately the writers have not been able to secure cultures of the fungus 
from Africa for inoculation on currant, although Putterill has courteously tried 
to secure more living material for this work. Under date of January 25, 1921, 
he writes as follows: 
“I have just returned from a visit to the infected trees at Vereeninging. Since my first visit there the 
trees have been more carefully treated, the diseased areas having been cut out and applications of coal 
tar made at regular intervals; I was unable to obtain fresh material for you." 
In spite of the fact that inoculations can not be made, there seems to be no 
ground for considering the African fungus different from that which produces 
the cane blight of currants. Mere distance between the localities can not be 
considered a reason for considering the fungi different, especially when they occur 
on cultivated plants which are known to be shipped and carry their parasites 
long distances. 
As to the possbility of this fungus being parasitic on apple in this country 
there is no evidence at present. Putterill’s letter would suggest that it is some¬ 
times not very virulent in South Africa since he was unable to find it in the orchard 
in which he had previously found it. That it can be made to grow on apple 
tissue is evident from the result of the inoculations made by Putterill on sound 
apples. Some years ago while checking up the results of shipping experi¬ 
ments on citrus for Rogers and Earle ( 8 ) the writers inoculated sound grapefruit 
with the currant cane blight fungus and produced a rot somewhat resembling the 
Diplodia stem end rot. 
Since B. ribis chromogena is an active parasite on currant, Stevens and Jenkins 
were able to prove the identity of the material which they collected from horse- 
chestnuts and rose with the cane blight fungus by actual inoculation experiments. 
This type of proof is not possible in the case of the saprophytic or nearly saprophy¬ 
tic form. There is, however, no reason to consider the nonchromogenic 
Botryosphaeria which occurs on apple in this country as specifically distinct from 
the non-chromogenic saprophytic Botryosphaeria on currant, since no morphologi¬ 
cal differences have been found. (See Table I, text figures 1, 2, and 3, and 
Plate 2, A, B, C, and K-N). 
