Feb. 15,1925 Root Rot of Grapevine Caused by Clitocybe Tabescens 347 
CULTURAL STUDIES 
Cultures made from the mycelial 
sheets on the roots of grapevines 
affected by root rot invariably yielded 
a very characteristic, slow-growing 
organism. Very scant growth of the 
fungus or none was obtained on corn- 
meal agar, and cultures on plain agar 
resulted in but weak growth. A much 
better growth was secured on prune 
agar and a very satisfactory growth on 
both maltose agar (30 gm. maltose per 
lifer) and raisin agar (50 gm. seeded 
raisins per liter). The growth of the 
fungus on these different media indi¬ 
cates that it does best on media rich 
in sugar. 
Since this organism develops rhizo- 
morphs that grow down into the agar, 
it was found highly desirable early in 
the work to have the culture media as 
clear as possible in order to best 
observe the development and morpho¬ 
logical characters of these structures. 
In order to clarify the agar, the whites 
of two eggs were added to each liter 
and the whole boiled prior to tubing 
and sterilization. 
The initial mycelial growth was 
whitish, the marginal growth in most 
cases being rather sparse and downy- 
appressed, although in a few instances 
a rather dense white marginal growth 
occurred (pi. 4, A). In all cases the 
mycelial growth eventually became 
thickened at the center, so that it 
presented a convex outline, the older 
portion near the center soon becoming 
a dirty white and later changing to 
isabelline or light buff. Often the 
immediate central part would appear 
as an irregular, light tan-colored lump. 
In the case of cultures made on raisin 
agar the agar invariably became dis¬ 
colored, showing dark brown immedi¬ 
ately beneath the mycelial mat and for 
some distance in advance of it. No 
such discoloration was noted, however, 
in any of the cultures on maltose agar. 
After the lapse of from two to three 
weeks, rarely longer, there would grow 
down into the agar, from the central 
part of the culture, peculiar, tortuous 
whitish strands, which constitute the 
beginning of rhizomorph formation 
(pi. 4, B). The plate cultures invari¬ 
ably dried up before the fungus 
attained any great development, so 
that their use was abandoned early in 
the work. Even tube cultures made in 
the size of tubes commonly used dried 
up as a rule before fruiting bodies 
developed. The best results with this 
slow-growing organism were obtained 
by making the cultures in large tubes 
and flasks. In some of the small-tube 
cultures a group of little hornlike 
processes—the primordia of clusters of 
mushrooms—often developed from the 
central part of the culture, but never 
developed further on account of the 
drying up of the cultures. 
On July 19, 1922, the fungus was 
inoculated on 4-inch lengths of roots 
of wild grape ( Vitis cor difolia Michx.), 
autoclaved in large test tubes contain¬ 
ing a small quantity of water. From 
the mycelial transfer, which was placed 
on the top of the root length, the 
mycelium quickly grew down through 
the inner bark, even to the bases 
standing in water. At a few points 
it pierced the bark and developed super¬ 
ficial masses of mycelium, a few light 
tan-colored nodules forming on the 
tops. 
Just a few days before the fruiting 
of one of these sets of cultures, the 
writer, while making a study of the 
grape diseases at Neosho, Mo., during 
the picking season, found several clus¬ 
ters of a caespitose species of mushroom 
developing from the bases of Moore’s 
Early and Concord vines which had 
been killed by root rot in a badly 
infected vineyard. Large numbers of 
clusters of the same fungus were ob¬ 
served also in one section of an oak 
forest (pi. 2) several miles distant, 
growing from the bases of dead oak 
trees and from roots beneath the sur¬ 
face of the ground. One large cluster 
was also observed growing from the 
superficial roots of an old silver maple 
shade tree in Neosho. The mor¬ 
phological characters and spore mea¬ 
surements of these specimens agreed 
perfectly with those of Clitocybe tabe¬ 
scens (Scop.) Bres., of which Morgan’s 
Agaricus monadelphus, Wilcox’s Cli¬ 
tocybe parasitica , and Murrill’s Mon¬ 
adelphus caespitosus represent the 
American forms. A representative 
specimen from both the vineyard and 
the oak forest was sent to Murrill, 
who identified both as Monadelphus 
caespitosus. 
Upon the writer’s return from Neosho 
he was agreeably surprised to find one 
of the series of cultures on the lengths 
of grape roots beginning to develop 
fruiting bodies. On August 10, a 
group of hornlike processes appeared 
on the top of the root length in one 
of the tubes. By August 17 this had 
developed into a miniature cluster of 
mushrooms that was reasonably typi¬ 
cal of those collected in the field a 
few days before. With the lapse of 
four more days the mushrooms of 
this cluster had attained their full 
development (pi. 4, C) and had cast 
on the side of the tube a print of white 
