686 
Journal of Agricultural Research 
Vol. XXIII, No. 9 
resistant. Cases were seen, however, in which actual contact with a 
diseased inflorescence produced a distinct canker covered with the 
typical gray mold. In one case observed such a spot completely girdled 
the stem, killing the parts above, including several flowering branches 
and leaves. Plate 4 C, shows a canker on a stalk. 
Unfortunately for the production of a crop of castor beans, the flower¬ 
ing parts of the plants are the most readily attacked by the fungus. A 
spike in any stage of development may become infected. If an abun¬ 
dance of the pathogene is present in the field and weather conditions are 
favorable, every spike will often become infected early in its develop¬ 
ment, even before the male blossoms have opened. More often, perhaps, 
infection takes place through the male blossoms. The anthers, water 
soaked as they often are after one of the summer rains or after a heavy 
dew, catch the spores of the fungus and permit them to germinate imme¬ 
diately and produce infection. Nearly mature spikes, containing only 
green pods, may become infected and fall over, maturing only a part or 
none at all of the beans. Usually a plant showed spikes in all stages, 
from buds just out of the sheath to nearly mature pods, all alike with 
evidences of recent infection. 
The castor bean is characterized by its possession of extrafloral necta¬ 
ries. These may occur at various places on the plant, often at the bases 
of leaf petioles, often on the leaf itself near the point of attachment of 
the petioles; but they are more numerous among the flowers. These 
nectaries exude nectar in large drops, which may be seen early in the 
morning before they have dried off. It was suspected that this nectar 
might favor infection by the fungus. Beneficial effect of nutrient mate¬ 
rial in the infection drop to infection by Botrytis has been mentioned by 
other writers (3) in connection with Botrytis cinerea Pers. Repeated 
examinations, however, failed to show that any large proportion of infec¬ 
tions occurred in contact with these nectaries. The part played by the 
nectaries, however, is not small. They attract myriads of insects, prin¬ 
cipally honey bees, wasps, bumblebees, and ants which may be seen 
crawling through the spikes, infected and healthy alike, especially after 
a shower when conditions are ideal for infection. These insects un¬ 
doubtedly play a large part in carrying infection. Whetzel ( 22 ) has 
noted such an insect relationship in connection with the spread of 
Botrytis paeoniae Oud. 
The appearance of a badly infected field in the height of the growing 
season is indeed discouraging in so far as crop prospects are concerned. 
Plate 2 B shows a castor bean plant in which practically every inflores¬ 
cence is affected. After the fruiting of the plant is thus arrested, new 
spurs shoot out with the brave intention of forming new blossoms. But 
almost invariably these new inflorescences which form throughout the 
summer sooner or later become infected. 
As the growing season draws to a close with the advent of cooler 
weather in the fall, the plant gradually ceases to make new growth and 
with freezing weather becomes greatly weakened or dead. After the 
leaves are shed, the remains of the diseased spikes, with a suggestion of 
the still recognizable mold, may be seen (PI. 5, A). Under the conditions 
of central Florida some life remained in many of the plants, and early in the 
spring with the gradually rising temperature, small, weak green spurs 
could be seen springing forth from various parts of the plants. Even 
earlier than this, however, evidences appeared of the overwintering of the 
fungus. On February 1, an inspection of the old plants standing in a 
