32 
BULLETIN 879. U. S. DEPARTMENT OF AGRICULTURE. 
This method is preferred chiefly because the preparation of the 
expressed juice requires time, and such extracts, unlike those from 
mosaic tobacco plants, lose their pathogenicity rapidly, usually 
having to be prepared fresh every day to insure success. In the case 
of the second method, fresh material is constantly available and its 
preparation takes little time. ^ 
Table IX gives results which are typical of inoculations by this 
method, but represent only a small fraction of the inoculations actu- 
ally made. 
Table IX. — Results of inoculations with the crushed tissues of mosaic cucumber plants. 
Treatment. 
Inoculum. 
Point of inoculation. 
Number 
of 
plants 
inocu- 
lated . 
Results. 
Date 
inoculated . 
Number 
of 
mosaic 
plants. 
Date last 
observed. 
Aug. 24, 1915. 
Do 
Inoculated... 
Control.. 
Inoculated . . . 
do 
Control 
Inoculated . . . 
Control 
Inoculated . . . 
Mosaic stem 
Base of stem 
do 
3 
3 
4 
6 
6 
5 
5 
12 
10 
12 
6 
6 
7 
7 
4 
4 
8 
8 
3 

4 
4 

3 

8 

7 
2 

5 

4 

5 

Sept. 2, 1915 
Do 
Jan. 22,1916 
Nov. 3f,1916 
Do 
Feb. 17,1917 
Mosaic leaf 
do 
Healthy leaf 
Mosaic leaf 
Healthy leaf 
Mosaic leaf 
do 
do 
do 
Jan. 31,1916 
Nov. 10,1916 
Do. 
Feb. 28,1917 
Do. 
Mar. 19,1917 
Do 
Do 
Mar. 11,1917 
Do 
do 
Base and tip of stem . 
do 
Mar. 15,1917 
Do 
Do 
Mar. 29,1917 
Do 
May 19,1917 
Do 
June 20, 1917 
Inoculated . . . 
do 
Control 
Inoculated . . . 
Control 
Inoculated . . . 
Control 
Inoculated . . . 
Control 
Mosaic stem 
Mosaic fruit 
Healthy fruit 
Mosaic leaf 
Healthy leaf 
Mosaic leaf 
TTealthy leaf 
Mosaic leaf 
Healthy leaf 
Base of stem 
do 
do 
Base and tip of stem. 
do 
do 
do 
Mar. 22,1917 
Do. 
Do. 
Apr. 9, 1917 
Do. 
May 30,1917 
Do. 
July 4, 1917 
Do. 
Do 
do 
RELATION OF INFECTION TO POINT OF INOCULATION. 
STEM INOCULATIONS. 
As shown by the preceding data, stem inoculations are successful* _ 
in most cases, regardless of the point of inoculation. Inoculations 
made in wounds produced by the removal of a leaf are ordinarily 
more effective than at other points, possibly because the virus comes 
more directly in contact with the vascular bundles at such points. 
LEAP INOCULATIONS. 
Inoculation of any green leaf will produce mosaic infection, but the 
inoculation of young leaves gives a much higher percentage of mosaic 
plants than the inoculation of leaves that have reached their full 
development. The point of inoculation in the leaf, however, seems 
to make little difference. , 
An interesting fact, already proved by Allard (5) for tobacco mosaic, 
is that infection can take place through the trichomes. He has shown 
that infection may occur if the trichomes of healthy plants are cut or 
pinched with instruments which have previously been dipped in the 
juices of a mosaic plant or when the mosaic juices are painted on the 
trichomes. Similar experiments have been made with the cucum- 
