A leaf disease of Walnuts. 
67 
The fungus has several times been isolated in pure culture by the 
dilution plate method and has been successfully grown for over a year 
upon various kinds of nutrient media. The conidia were found to germinate 
more readily in water than in nutrient agar. In the process of germination 
the cells first become distended from the water which they have absorbed, 
and consequently are more or less constricted at the septa. From each 
cell, when cow-pea agar is used, one or more germ tubes arise, which 
rather tardily develop into a much branched, septate mycelium. Within 
48 hours the hypliae will not have reached 
a greater length than about 100 microns 
(fig. 6) and the colonies may be visible 
to the eye only at the end of four days. 
Growth proceeds slowly and the colonies, 
which are dark olivaceous in color, will 
not have attained a size greater than half 
the area of a pin’s head within three 
weeks or a month. Conidia are readily 
formed upon this medium, however, and 
have been observed eight days after the 
plates were poured. They are successively 
abstricted from short mycelial branches 
(fig. 5), but are indistinguishable from 
conidia formed in acervuli (fig. 4). In 
culture the mycelium becomes divided into 
chains of rounded, thick walled cells as 
shown in fig. 3. 
When conidia are germinated in drops 
of water, in van Tieghem cells or on glass 
slides which have been placed in moist 
chambers, the hypliae quite commonly 
anastomose, as represented in fig. 1. This 
phenomenon is not uncommon with germi¬ 
nating spores of various fungi, and has Fig. l. Conidia of Cyimdrb- 
been noted by several investigators, the sporium fiigiandis anastomosing and 
most extensive observations having probably forming secondary conidia, in water, 
been made hv RrffftdI) Tt'lias been culture, 24 hours old. 
oeen maae oy Krefeld ) it lias oeen F ig. 2. An acervulus in ver- 
observed by Jarius 1 2 3 4 ), while investigating tical section. 
the conidial stage of Sphaerella pinoides Fig. 3. Mycelium in old culture. 
(Berk, et BlOX) Nissig) and by Stone *>4. Conidia from an acervulus. 
while investigating the ascogenous stage*). 
F»Ot uncommonly too, one notes that se- Fig. 6. Germination on cow-pea 
condary conidia as shown in fig. 1, may agar, 48 hours old. 
be formed in water culture. 
Thus far attempts to induce this fungus to develop an ascigerous 
stage in culture have been fruitless. Even when affected leaves were 
1) Brefeld, 0 ., Untersuchungen usw., 4, 116, pi. 9, fig. 14. 
2) Jarius, M., Ascochy ta Pisi bei parasitischer und saprophy tischer 
Ernährung (Bibi. Bot. 1896, 34, 1—45, pi. 1). 
3) According to Saccardo, P. A. (Syll. Fung. 1913, 22, 120). 
4) Stone, R. E., The life history of Ascochy ta on some leguminous 
plants (Ann. Mycol. 1912, 10, Nr. 6, 564—592, pi. 19—20). 
5* 
