^pr. ax, X923 
Gummosis of Citrus 
215 
distances, ranging from 5 to 60 cm. above the '‘bud union.'' With every 
inoculation a similar cut, to serve as a control, was made in the opposite 
side of the same tree. A sheet of paraffined paper was then tied against 
the surface of the bark over each cut and fastened with wax at the 
upper edge to exclude rain and dust. 
The different kinds of inoculum and the number of trees were as follows: 
(i) Small pieces of sound bark and wood, four trees; (2) bit of diseased 
bark, two trees; (3) small bits of wood permeated with gum from outer 
gummous zone, two trees; (4) small portion of exuded gum, one tree; 
(5) bits of dead bark containing Penicillium roseum Lk., two trees; (6) 
hyphae and spores of Botrytis cinerea, taken from rotting diseased bark^ 
three trees. 
None of the inoculations with sound wood or bark, gum-filled wood 
from the outer gummous zone, or exuded gum produced any gumming 
or development of disease. All the inoculations from diseased tissue, 
however, showed gum exudation within 2 to 4 months, and in 
one case a lesion 8 by 15 cm. developed in 9 months. One of the 
inoculations with Penicillium roseum showed slight gum exudation in 
4 months without development of a lesion, but the other cut healed 
without gumming. All three of the Botrytis inoculations resulted 
in gummosis of the same type as that from which the fungus was 
obtained. In one of them slight softening of the bark was noted in 
10 days. A softened area of bark which measured 8 by 2.5 cm. in 50 
days (with fruiting of Botrytis on the surface) had increased to 10 by 
4 cm. in 4 months, with copious exudation of gum some of which was 
exuding through cracks 50 cm. directly above the cut in the outer 
noninfected gummous zone. About i year after this inoculation the 
space over which the bark was dead to the wood measured 10 by 2.5 cm., 
and this was surrounded by an irregular area over which only the outer 
bark was killed, making the entire area 30 by 27 cm. Botrytis was fruit¬ 
ing at various places over this area. 
A second set of experiments was then carried out. These were planned 
to test the influence of various kinds of wounds, the influence of obstruc¬ 
tions in the sap current, and finally, the influence of continued pressure 
Upon the bark. These experiments were made in July, 1912, on sound 
trunks of 19-year-old Lisbon lemon trees at Santa Paula. The follow¬ 
ing methods were used both with and without contamination with oure 
cultures of Botrytis cinerea: Cuts vertically or horizontally through the 
bark, auger holes with and without glass or wooden plugs, bruises made 
by light and heaVy blows from hammers, wounds made by slicing off 
both thin and thick layers of bark, wounds made by entirely cutting off 
large areas of the bark and so forth. Constant pressure was also exerted 
against the bark with wooden blocks tightened by means of screws in an 
iron collar. 
It was difficult to make these inoculations or injuries in tree trunks in 
the open and keep them absolutely Jree from organisms. In attempting 
to overcome this difficulty the following method was adopted for the 
most important of these experiments. A cloth hood to be tied to the 
tree trunk was made by fastening a piece of fumigation-tent cloth to a 
wooden barrel hoop severed on one side. Strings were fastened to the 
cut ends of the hoop and to the comers of the cloth opposite the hoop. 
The hoop was allowed to hang down. The upper strings were tied to the 
trunk of the tree just below the branches and the hoop was fastened 
