12 ‘‘ ROUGH-BARK ’’ DISEASE OF YELLOW NEWTOWN APPLE. 
those growing on either fruit or branches; in fact, this form of spore 
is rather difficult to find in pycnidia from leaves. For this reason 
the fungus as it appears on leaves may easily be mistaken for Phoma 
malt Schulz. and Sacc. On apple wood and fruit pycnidia produce 
both spore forms in abundance, some of them producing only one form, 
while others produce both. A localization of the production of the 
two kinds of spores in separate portions of the same pyenidium, as 
mentioned by Diedicke, has never been observed. 
The fungus seems to differ essentially from other fungi described 
as occurring on the apple. Phoma mali Schulz. and Sacc., shown by 
Lewis! to cause a canker and soft rot of the apple, resembles it in 
the size of spores and growth on certain media, but differs from it 
in the absence of secondary spores, in the structure of the pyenidium, 
and in having less tendency toward stroma formation. The reac- 
tions of the two fungi toward certain culture media are also very 
different. 
Fusicoccum viticolum, described by Reddick? and shown by him 
to cause a disease of the grape, resembles this fungus in the pro- 
duction of two similar spore forms, but differs from it in the 
size of spores and in that the pycnidia consistently develop in a 
stroma. 
Phomopsis citri, described by Fawcett? as the cause of a stem-end 
rot of citrus fruits, differs materially from this fungus both in pyenidial 
and spore characters, as does also the pyenidial form of Dzaporthe 
batatatis, as set forth by Harter and Field,* though both of these are 
evidently closely related to this fungus. 
Accepting Saccardo’s conception of the genus Phomopsis and 
Diedicke’s investigations of the genus, the fungus in question is 
clearly a Phomopsis. 
Of the described species of this genus the fungus resembles most 
closely Phomopsis ambigua (Nits.) Trav., described as occurring on 
the pear in Europe, but differs from it in having much larger sec- 
ondary spores and is apparently different in other characters, though 
it is difficult to tell from the meager published description. Further- 
more, Phomopsis ambigua is described as the imperfect form of 
Diaporthe ambigua Nits., associated with it on the pear, but no species 
of Diaporthe has ever been found in connection with this fungus. 
1 Lewis, C. E. Apple diseases caused by Coryeum foliicotum and Phoma mali. Maine Agricultural 
Experiment Station, Bulletin 170, 1909. 3 
2 Reddick, Donald. Necrosis of the grapevine. New York (Corneil) Agricultural Experiment Station, 
Bulletin 263, 1909. 
3 Fawcett, H. S. The cause of stem-end rot of citrus fruits (Phomopsis citri 7. sp.}. Phytopathology, 
v. 2, p. 110-113, pl. 8-9, 1912. 
4 Harter, L. L., and Field, E. C. Diaporthe, the ascogenous form of sweet potato dry rot. Phyto- 
path slogy, v. 2, p. 121-124, 4 fig., 1912. ; 
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