378 [ ASSEMBLY 
ASU 
into the body of the drop of gum. It having been suggested that 
the gum might have appeared had no virus been applied, another 
set of inoculations was tried (exper. 144 to 147) in which two punc- 
tures about four inches apart were made on each shoot, one of which 
was wet with a drop of pear blight infusion and the other not, To 
detect any possible influence of the upward movement of the sap, 
in two cases the wound nearest the end of the branch was infected, 
in the other two cases the wound farthest from the end of the 
branch. The results were uniform; the infected wounds gave a drop 
of gum, and the others did not. Three of these branches were ex- 
hibited before the Botanical Club of the American Association for 
the Advancement of Science at its meeting in Philadelphia, with a 
statement of the case. 
PrEAcu. 
No. of Part Source } Days of 
experiment. treated. of virus. incubation. 
Peon ath Gay oat Pipe phere pass aptly as Stem. Pear. 10 
ETE ESR Gem LSE a Srp ty ays Ss ‘ ie 6 
54D ‘ : 6 
PSD) 5 Sieh Sei ple (cole a lane be SSE peated <s 6 
55b a 4 6 
55c E es cS 6 
144 66 66 5 
145 y ce ns 4s 
146 66 6“ 5 
147 : < 5 
Having now presented the various sides of the matter, I think we 
may safely conclude, taking all the facts into consideration, that the - 
abnormally large production of gum in the peach and kindred trees 
is due to the inciting influence of a fungus, possibly bacteria, but 
more probably a filamentous fungus,and that it is not necessarily 
restricted to a single species. 
The flow of gum is often a serious drain upon the vigor of the 
tree, and it becomes an important question what shall be done to 
stop it. Frank and Prillieux recommend cutting away entirely such 
small branches as are affected,and in larger branches cutting out 
the spots producing the gum. This is not always practicable, however, 
as for example in the following case. In looking over an orchard 
not far from the Station, trees were noticed which from one point of 
view were completely covered from the ground to the ends of the 
limbs with masses of gum averaging the size of a hazel nut, but on 
stepping to the opposite side of the tree the bark appeared normal 
and no gum visible. Upon inquiry it was learned that an exception- 
ably violent hail storm had passed over that part of the orchard 
early in the season, and that it came so that hailstones struck on the 
side of the trees now covered with gum. It was plain that the gum 
had started wherever the bark was injured by the hail. The knife 
could certainly not be used to advantage in this case. A trial of 
