8 
Journal of Agricultural Research 
Vol. XIV, No. x 
same field. Sections of diseased tissues from various parts of blighted 
plants were externally disinfected, and then plated on various types of 
nutrient media. The plates were incubated at various temperatures 
until organisms began to develop on the plates. Each type of organism 
was then transferred to agar slants, and grown in pure culture until its 
characteristics had developed. Both bacteria and fungi were isolated 
from various tissues of blighted plants. Plants in more advanced stages 
of blight yielded an abundance of organisms, while tissues from some of 
the plants in early stages of the disease remained sterile on the plates, 
thus indicating that no microscopic organisms were present in the tissues. 
Examination of the various cultures showed that some common organisms 
including species of Alternaria, Eusarium, Verticilium, Rhizoctonia, and 
Macrosporium were present, together with various of the lower soil fungi. 
Bacteria of numerous types and colors were also isolated from diseased 
tissues, but none of these appeared different from the common-soil 
and decayed-plant-infesting organisms. Subcultures of these organisms 
were prepared for inoculation work in the field, and with these a number 
of healthy field plants were inoculated by pricking the organism into the 
healthy tissues. A sufficient number of plants were used as controls. 
The inoculated plants and controls were under observation for a long time, 
but in no case did any of the inoculated plants consistently show a higher 
percentage of blight than the controls. These results led to the conclusion 
that none of the organisms which had been isojated in the laboratory 
from blighted plants was the specific cause of spinach-blight. The fact 
that the tissues from certain of the blighted plants, when externally 
disinfected and plated, remained sterile indicated that the disease could 
occur in a plant without any microscopic organism being associated 
with it. Therefore these results confirmed those of previous workers to 
the effect that spinach-blight is a definite disease, and is not due to any 
specific microscopic organism thus far obtained. 
methods employed in the spinach-blight experiments in 
1916-17 
The cages used in the first experiments were furnished by the United 
States Department of Agriculture, but they were found to be too large for 
convenient work. The door was small, and the operator did not have 
room to reach conveniently to the comers of the cage. Therefore the 
cages used later 1 were smaller, the dimensions being 2% by 3 by 2 feet; the 
frame was made of i-inch material and the door occupied one whole side. 
This made an arrangement whereby the operator had access to all parts of 
the cage; yet the cloth was draped around him sufficiently to eliminate the 
possibility of the insects' gaining entrance through the large opening 
(PI. 5, A). The door and manner in which it is made is shown in Plate 
1 The writers wish to acknowledge the suggestions of Mr. J. B. Norton, of the Office of Cotton, Truck 
and Forage-Crop Disease Investigations, Bureau of Plant Industry, in the development of the same. 
