THE MOSAIC DISEASE OF CUCURBITS. 
31 
inoculations were made in the stems, leaves, and in some cases in 
the fruits. In the earlier experiments a sterile hypodermic needle 
was used for inoculation and the inoculum injected rather deeply 
into the stem. It was found, however, that inoculations made by 
cutting off a leaf close to the stem and then pricking the inoculum 
| into the wounded surface gave a higher percentage of infection. In 
leaf inoculations a drop of the inoculum was pricked into the leaf at 
various points with a sterile needle. The results of inoculations by 
these methods are shown in Table VIII. 
Table VTII. — Results of inoculations iviih the expressed juices of mosaic cucumber plants. 
Treatment. 
Inoculum, 
expressed juice 
of— 
Point of 
inoculation. 
Num- 
ber of 
plants 
inocu- 
lated. 
Results. 
Date 
inoculated. 
Num- 
ber of 
mosaic 
plants. 
Date last 
observed 
Aug. 2, 1915 
Do 
Inoculated... 
Control 
Inoculated . . . 
Control 
Inoculated . . . 
Control 
Inoculated . . . 
Control 
Inoculated... 
do 
Control 
Inoculated... 
Control 
Mosaic plant 
Base and tip of stem. 
..do 
4 
3 
5 
3 
8 
5 
8 
6 
11 
7 
8 
6 
3 

3 

8 

5 

5 
6 

5 

Aug. 17,1915 
Aug. 20,1915 
Aug. 14,1915 
Do. 
Aug. 4, 1915 
Do... 
Mosaic fruit 
Young leaf and base 
of stem. 
do 
Aug. 21,1915 
Do 
Mosaic fruit 
Healthy fruit 
Base of stem 
do 
Sept. 2,1915 
Do. 
Nov. 19, 1915 
Mosaic leaves 
Nov. 26,1915 
Do 
Do. 
Nov. 28, 1915 
do 
Dec. 6, 1916 
Apr 8, 1916 
Do.. . 
do 
Base of stem 
do 
Apr. 20,1916 
Do. 
Sept. 6,1916 
Do 
Mosaic plant 
do 
....do 
Sept. 15,1916 
Do. 
TESTS WITH CRUSHED TISSUES OF MOSAIC PLANTS. 
In later work, experience proved that the easily prepared crushed 
tissues of mosaic plants formed a more constantly virulent inocu- 
J.um than the expressed juices. Infected portions of the plant, 
either fruit, stem, or leaves, were crushed in a sterile dish after they 
had been cut into small fragments with sterile scissors or a scalpel. 
This material was inserted in a small cut in the stem made with a ster- 
ile scalpel. Such wounds were usually made in the lower portion 
of the stem, in some cases directly below the oldest leaf, but more 
commonly a leaf was cut off close to the stem and the incision made 
in the cut surface. A longitudinal cut, 3 to 5 millimeters long and 
2 to 3 millimeters deep, was found sufficient, the small piece of crushed 
material being inserted in the wound, which healed rapidly. In 
other cases a small incision was made at the tip of the stem directly 
£.below a young leaf and a fragment of the crushed tissue inserted at 
this point. Inoculations with crushed material at either of these 
points, or both, ordinarily gave a slightly greater percentage of infec- 
tion than was obtained by the injection of the expressed juices. It 
was found also that inoculations at two or three points were more 
generally successful than where a single inoculation was made. 
