CITRUS MELANOSE AND ITS CONTROL 19 
as ethyl alcohol, ether, acetic acid, mercuric chloride, hydrogen 
peroxide, and in many instances the parts to be cultured were washed 
in alcohol or ether for a second or two and transferred to mercuric 
chloride for varying lengths of time and rinsed in sterile tap water. 
Whenever fresh hydrogen peroxide was used, washing of the "ster- 
ilized parts was dispensed with; however, many cultures were at- 
tempted without the use of surface disinfection. The sterilizing 
agents were used with caution to prevent the chance of killing the 
causal organism within the host if it were present. Fully 1,000 
attempts were made, but not in a single instance was the causal organ- 
ism recovered. On the other hand, this fungus can be cultured 
readily from dead citrus twigs and from citrus fruits affected with 
stem-end rot, as well as from the surface of normal tissue. 
GROWTH ON ARTIFICIAL MEDIA 
Phomopsis citri grows on a rather wide range of culture media, 
but on some the mycelial growth is sparse, whereas on others it is 
abundant. The media used most often in these studies have been 
corn-meal agar, potato-dextrose agar, steamed stems of pigeon pea 
(Cajanus indicus), sweet clover, grapefruit, and sweet potato. 
On corn-meal agar the fungus makes a rapid white growth, mostly 
a sparse mat on the surface with a small amount of aerial mycelium. 
Though not abundant, sporulation on this medium occurs within one 
to four weeks in quantities satisfactory enough for general use. 
On potato-dextrose agar there is an abundant, rapid mycelial 
growth, at first snowy white, darkening somewhat with age; aerial 
parts fairly abundant and usually fluffy, but at times compact. It 
sporulates sparsely on potato-dextrose agar, and in many cultures 
pycnidia fail to develop. 
On beef -peptone agar the mycelial growth during the first week 
or 10 days is very similar in quantity to but somewhat more velvety 
in appearance than growth on potato-dextrose agar. 
On steamed stems of sweet potato, pigeon pea, sweet clover, and 
grapefruit P. citr-i makes a rapid mycelial growth, and in a short 
time the stems are covered with white mycelium. At first the 
growth is flocculent, but as the stems dry the mycelium usually 
becomes compact, and within 10 days or two weeks at favorable tem- 
peratures distinct evidence of pycnidial development is seen. Later 
these pycnidia become more erumpent (pi. 8, A), and still later 
cream-colored spore tendrils emerge (pi. 8, B). Ordinarily from 
two to six weeks are required to develop a crop of spores at room 
temperature. 
In addition to the above-mentioned media P. citri grows abun- 
dantly on such media as Blakeslee's agar, Leonian's agar, carrot agar, 
peptone-dextrose agar, potato hard agar, prune agar, and shredded- 
wheat biscuits. It grows sparsely on beech-twig agar, Cohn's agar, 
Czapeck's agar, Ferni's agar, and Uschinsky agar. The organism 
has also been grown on broths of prune, peach, sweet potato, tomato, 
potato, orange twigs, and apple twigs. 
The rate of growth of this fungus varies considerably, depending 
upon the medium. On certain media the rate of growth is at first 
slow for a few days and later is very rapid, but for the most part it 
may be considered a fairly rapid grower. 
