192 
B. B. Higgins, 
began to appear on the inoculated leaves and by the end of eight days 
nearly every leaf showed one to six spots. Each spot contained numerous 
pycnidia which bore pycnospores exactly similar in shape, size etc. to 
those found the previous summer. 
To learn the time necessary for infection the check plant was now 
inoculated with pycnospores from the first plant. Again spots began to 
appear on the fifth day. This showed clearly that the infections developed 
from the inoculations rather than from pycnospores which had lodged on 
the plants during the previous summer; because had such pycnospores 
been on the plants, they would have produced infections during the first 
two weeks the plants were under bell jars. 
Systematic. 
Neither the perfect nor imperfect stage of the fungus so far as I 
can find has ever been described. Apparently no similar ascomycete has 
been described on Prunus pennsylvanica and the only one described on 
the genus Prunus , whose asci and spores are similar in size, is Sphae- 
rella cerasella (Aderh.) Sacc. et Syd. 1 ) whose imperfect stage is Cerco - 
spora cerasella Sacc. according to Aderhold 2 3 * * ). 
The presence of a Septoria stage and the carpogonical structures 
suggested a near relation to Gnomonia erythrostoma Pers., but a com¬ 
parison of the fungus with descriptions of this genus show at once that 
they are distinct. They differ in shape and size of perithecia, in form of 
asci, and in their effect on the host. The affected leaves drop prematurely 
instead of hanging on the tree all winter as in Gnomonia erythrostoma. 
The shape of the perithecium with the very short beak, and the absence 
of a pore and thickened apex in the ascus would place the fungus in 
Sphaerella rather than Gnomonia. Since the fungus agrees with the 
genus Sphaerella Ces. et de Not. it is placed in this genus; and I pro¬ 
pose the name Sphaerella nigerristigma with the following diagnosis. 
Diagnosis. 
Mycosphaerella' 6 ) nigerristigma n. sp. Perithecia black, amphi- 
genous but mostly epiphyllous, aggregated on spots killed by pycnidial 
mycelium or scattered over the entire leaf, ovate, 90—110 x 45—85 ju, 
immersed with the short beak protruding through the leaf epidermis; 
asci cylindrical, clustered, aparaphysate, without a pore in the apex, 35 
—45 x 7 g, spores fusiform colorless, once septate 16—21 x 2,5—3 g, 
Pycnidial stage: Spots at first glaucous but soon turning brown, 
often dropping out, 2—5 mm in diameter; pycnidia colorless or light 
brown, amphigenous, immersed, globose, with a single large apical pore; 
1) Saccardo, Sylt. Fung. 16, p. 469, 1902. 
2) Aderhold, R., Mycosphaerella cerasella n. spec., die Perithecien- 
form von Cercospora cerasella Sacc. und ihre Entwicklung (Ber. D. Bot. Ges. 
18, p. 246—249, 1900). 
3) The technical description bears the genus name My cosphaerella Johanson 
(Svamper frâm Island; Ofversigt af Konigl. Yetensk. Akad. Vöhandl., p. 163, 1884) 
which is used by Schroeter (Crypt. -Fl. Schlesien 32, p. 332, 1897), by Lindau 
(Engler u. Prantl, Natürl. Pflanzenf. 1, p. 423, 1897), and by many others, 
though it is desirable that Sphaerella Ces. et de Not. may be one of the genera con- 
servanda adopted by the Botanical Congress in London, 1915. 
