TEAR-STAIN OF CITRUS FRUITS. 7 
In the fall of 1919 a more extensive test was conducted. Fifteen 
lots of fruit were involved. Five of these lots were selected by the 
writer, and the remaining ten lots were selected in various parts of 
Florida by persons specially chosen for their competence to select 
typical rust-mite injury and typical wither-tip tear-stain. Each 
of these lots was sorted into several groups of one to four fruits 
each according to the variety of fruit, the particular type of effect, 
and the intensity of it. For a comparative study, cultures were 
made from fruits in the same lot that were free from blemishes or 
from unblemished areas on the russeted or tear-stained fruits. One 
hundred bits of tissue, approximately 1 square millimeter in surface 
area, were cultured from each test area of each fruit, using 10 Petri 
dishes, each with 10 bits of tissue. The results when reduced to a 
percentage basis, as in Table III, also represent the average numbers 
of occurrence per fruit. Corn-meal agar was used as a culture 
medium and the plates were held six days at room temperature. 
Counts were made of the common saprophytic type of Cladosporium 
as well as of Colletotrichum colonies. Bacteria and fungi other 
than these were reckoned as miscellaneous. Two parallel series 
were made, one for undisinfected tissue and one from similar areas 
on the same fruits washed with a disinfectant. Bichlorid of mercury 
solution (1 to 1,000) was used for 1 minute with subsequent rinsing 
on all disinfected lots except K, L, and M; on these three lots undi- 
luted fresh hydrogen peroxid was used without rinsing. Table III 
gives the results, with fractions omitted for the higher percentages. 
Table III shows that Colletotrichum c;loeosporioides is practically 
universally distributed on citrus-fruit surfaces and that it escapes to 
a considerable degree the surface disinfection process ordinarily prac- 
ticed in culture work. It is present about equally on the average in 
tear-stained and russeted areas. The amount varies in different lots 
of fruits, but seems to be more abundant where the visible effects 
are most pronounced. A saprophytic type of Cladosporium is isolated 
with the same constancy as Colletotrichum gloeosporioides, but with 
less frequency. These extensive culture tests show, therefore, that 
it would be about as reasonable to ascribe the blemishes to one of 
these organisms as to the other, if constancy of isolation from lesions 
is to be the deciding consideration. However, neither fungus reaches 
a frequency of occurrence high enough to justify holding it to be 
the causative organism on this evidence alone. 
Certain fruits having the melanose type of tear-streak were 
selected, and cultures were made from these in the manner already 
described, comparative tests being made from unblemished areas, 
from melanose tear-streak, and from diffused melanose areas; and 
cultures from the surface blemish known as "shark skin" were also 
made. The results are given in Table IV. 
