464 
Journal of Agricultural Research 
Vol. VIII, No. 13 
In this experiment the seedlings of Lot I were slightly diseased (0.011 
per cent), the results being comparable with those obtained from the 
field planted on April 20. It is improbable that the diseased plants in 
the field planted with these seed on May 15, which varied from 2.7 to 8.1 
per cent of the plants of single rows, were due to seed infection, but rather 
to the spread of the disease from other infected plants at an extremely 
favorable time. 
The other results obtained, 0.2, 0.14, and 0.31 per cent, do not account 
for the amount of disease observed in fields planted with these seed. 
The field planted with seed of Lot V was the most badly diseased of any 
seen on a trip about the State in June; and, while the author obtained 
only 142 seedlings, none of them were diseased. 
Without doubt, 0.46 per cent of diseased seedlings at the beginning of 
a season, especially if rainy weather prevails before chopping, would be 
sufficient to start a general field infection, and this could be called the 
primary infection. It is interesting to note in this connection, however, 
that 1,218 seedlings grown in the greenhouse from seeds planted on 
August 5 and taken from the same bag as those in Lot VII were entirely 
free from the disease as late as August 29. It is improbable that the con¬ 
ditions in the greenhouse were unfavorable to the development of the 
disease, since successful artificial inoculations have been made here 
besides the two cases of natural cotyledonary infection already mentioned; 
and, if we accept this as the case, adding these seedlings to those observed 
in the field, making a total of 7 diseased seedlings in 2,708, the 0.46 
per cent is reduced to 0.25 per cent. 
Whatever the true situation in this regard may be, and only further 
carefully checked observations can decide, it is a fact that the disease 
appears sooner in some parts and later in others, yet almost inevitably 
in every cotton field. In any method of primary infection it is im¬ 
probable that every plant will be attacked, so that the spread of this 
disease from leaf to leaf and plant to plant becomes a subject of consid¬ 
erable interest and importance. 
INSECT DISSEMINATION 
In view of all the work—much of it recent—done on the subject of 
the spread of plant diseases by insects, an effort was made to determine 
carefully the extent of their activities in the dissemination of the angu¬ 
lar leafspot. Leaf-eating beetles (flea beetles and cucumber beetles) 
were abundant in some fields of seedling cotton, but in only one case 
has the author observed the disease developing about the margin of 
eaten areas. The most common insects upon the older plants were the 
jassids; and, since they were more active than any other except the 
ants (the latter, however, being active only after the dew had disap¬ 
peared), especial attention was given them. Five large plants were 
