Feb. 23,1924 
Life History of Grape Rootrot Fungus 
611 
inoculated on October 18, 1920, with ascospores from the fruiting heads. 
In two days numerous spores germinated. Growth was slow, the germ 
tubes having reached a length of not more than 20/*. Viala and Pacottet 
(35) described fairly accurately the method of germination, showing that 
a few spores became septate during germination but more of them were 
undivided. Single spores were marked in the plates, and when they had 
germinated each spore was transferred to a tube of slanted corn-meal 
agar. All of the writer's cultures discussed in this paper were derived 
by transfer from these single ascospore cultures. Eight single spore 
cultures were made and kept at room temperature until the mycelium 
had made good growth, and they were then placed in a refrigerator 
where the temperature averaged 10 to 12 0 C. This provided uniformly 
cool, moist and dark conditions for growth. 
corn-meal agar cultures 
On the corn-meal agar the fungus grows slowly forming a thin layer of 
felty mycelium, white to buff at first, becoming green at the center, the 
green color gradually spreading over the surface. It becomes blackish 
green with age, sometimes taking on a grayish tinge. None of these first 
transfers fruited, but later transfers were made to the same medium, 
making in all 28, and at the end of five months stalked fruiting bodies 
were found on three cultures, one culture having three at the base of the 
agar. These were small and white or grayish white ascocarps with 
heads scarcely wider than the stalks. The heads contained asci and 
paraphyses which were slender and extended out beyond the asci. 
OATMEAL PASTE AGAR CULTURES 
Agar in which the nutrient medium is an oatmeal paste was found 
very satisfactory for the development of Roesleria. Forty-five transfers 
were made at different times from single ascospore cultures to tubes of 
this medium; 37 of these were kept at least part of the time in the 
refrigerator at io° to 12 0 C. The mycelium spreads very slowly, forming 
a compact growth, cream or buff colored at first which becomes a bright 
malachite green, darkening with age. The growth is more felty, more 
luxuriant, and of a brighter green than that on the corn-meal agar. 
In from five to seven months ascocarps appeared in a large number of 
the tubes. They occurred singly or in groups of from 2 to 15 (PI. 1, 
B, F, G). The stalks were white to grayish with mouse-gray heads. 
These fruiting bodies, 4 to 4-^ mm. X 1 mm. were somewhat larger than 
those occurring in nature on the roots, the stalk being thicker and the 
heads larger, 3 mm. wide in the largest ones. 
cultures on apple roots 
Transfers were made from each of the single-spore cultures to auto¬ 
claved apple roots in large test tubes, with a few cubic centimeters of 
water in the bottom. These cultures were kept in the refrigerator at 
10 to 12 0 C. The fungus grew well, covering the roots with a felty or 
fluffy mycelium, white to buff at first, later becoming bright malachite 
or fluorite green (Ridgway) . 4 In from 6 to 12 months, when the cultures 
had dried somewhat, fruit bodies containing mature asci appeared 
4 Ridgway, Robert.— Color standards and color nomenclature:. 43 p., <53 col. pi. Wash¬ 
ington, D. C. 1912. 
