1916] 
DUGGAR—RHIZOCTONIA SOLANI 3 
ferentiated peripheral layer; and (7) cultures readily ob- 
tained from mycelium or sclerotium, the organism producing 
in culture only mycelium, flake-like masses or tufts, and ef- 
fuse sclerotia. 
In reviewing the earlier of these studies upon diseases of 
this type which may be caused by Rhizoctonia it is hazardous 
to attempt to interpret those cases in which the organism is in- 
adequately described, yet bearing in mind the more striking 
characteristics of Rhizoctonia, it is believed that no litera- 
ture is here included which does not suggest this fungus. In 
the later studies the organism has been for the most part so 
well described that little doubt may be entertained with re- 
spect to the determination. For the present it is necessary to 
rely upon a discussion of the literature, but when more ma- 
terial, in the form of cultures, from the regions here referred 
to is available, a supplementary statement will be required. 
An examination of the files of the more important of the 
horticultural journals of both France and Germany prior to 
1880, has been made with the result that references to dis- 
eases of cuttings and seedlings are found to be not infrequent, 
but without exception these contribute nothing, so far as I 
have been able to find, which will throw light upon the organ- 
ism concerned. The earliest reference which has been found 
to be of importance is that of Therry and Thierry ('82). 
They reported having studied, for more than a year, the my- 
celial filaments which invaded Ше cutting-benches of garden- 
ers and florists in the region of Lyons. Although unable to 
find a spore stage, they described the organism studied as 
Mortierella arachnoides Th. & Th. (araignée des serres), 
since they considered the vegetative stage to show a close re- 
lationship to M. Ficariae which they found on leaves of Ficaria 
Ranunculoides. M. arachnoides is described as killing the 
shoots and growing over the fallen tissues, disorganizing them 
with great rapidity, also growing over the soil in the form 
of a web of strands. The mycelium is said to be able to grow 
meters during a single night. The points noted, together 
with the brief description of the mycelium, strongly sug- 
Tü ae a on 
