POTATO FAILURES. 
9 
7. On August 1st, pure culture of the fungus was placed on five 
tuber-stems and the cultures were covered with wax. These stems were 
examined on August 15th, and it was found that the fungus had pro¬ 
duced marked wounds on all of them. Two of these stems which were 
practically cut off are shown in Plate XI. Fig 2. Two of the five stems used 
for a check were slightly colored under the wax but no traces of the dis¬ 
ease were found. 
These experiments show that the attacks of the fungus 
may produce the abnormal development of the potato plant, 
so common to many of our fields. 
It is evident if fungus injuries are responsible for such 
peculiar development of the plant that mechanical 
injuries ought to produce similar results. Accordingly a 
series of experiments was planned to test these points. 
Mechanical Injuries. On August 24th, all of the tubers 
were removed from forty plants. September 2d, the tubers 
which had formed during this time were removed and many 
of the roots were injured. All the plants soon took on the 
peculiar development described above and 29 of them devel¬ 
oped “ Aerial Potatoes.” These plants were dug Septem¬ 
ber 20 and it was found that many of them had produced 
typical ‘‘Little Potatoes.” (See Plate X.) Examinations 
failed to reveal the presence of Rhizoctonia on any of these 
plants. Check plants growing by the side of those used 
in the experiment produced normal tops and tubers. 
On the same day, a ring of outer tissue about one half¬ 
inch wide was removed from around the main stem of 
twenty-five plants. These plants also took on the peculiar 
top development and all produced aerial tubers. Plate IX. 
shows a fair specimen of this lot of plants. Twisting the 
stem and wrapping a wire firmly around the stem gave 
similar results. 
THE SEED. 
During the past spring, the Department made a num¬ 
ber of observations on the percentage of infected Rhizoc¬ 
tonia tubers in different lots of potatoes offered for sale as 
seed. One lot examined contained 805 tubers. Ninety-one 
per cent of these were infected with the disease 
and were more or less covered with sclerotia. 
While the remaining nine per cent were free from the 
sclerotia, careful examination with the microscope revealed 
the fact that the eyes of most of these tubers harbored a 
few strands of the fungus. Five of the supposed clean pota¬ 
toes were placed in a moist chamber and at the end of two 
weeks, there was an abundance of this fungus on three of 
them. The other two were completely overrun with Fus- 
arium and no traces of Rhizoctonia could be found. The 
