24 
Journal of Agricultural Research y 0 i. xxxi, no. i 
Table X .—Results of artificial cross inoculation of healthy cucumber plants with 
crushed leaf tissue of mosaic milkweeds 
Date 
(1920) 
Source of inoculum 
Location of inoculated 
plants 
Number 
of plants 
inocu¬ 
lated 
Number 
of mosaic 
plants 
Date 
ob¬ 
served, 
1920 
Aug. 6_ 
Rockland, Wis_ 
Greenhouse 
g 
3 
Aug 12 
Do_ 
__ __do____ 
__do.° 
g 
0 
Aug. 18 
Do_ 
.do. _ __ 
Field_ 
12 
g 
Aiig. 12 
Do_ 
.do. __ 
do.® 
7 
0 
Aug 18 
Aug. 12_ 
Madison, Wis_ 
Greenhouse . 
7 
7 
Sept- 1 
Do_ 
_do_ 
do.® 
5 
o 
Do 
Aug. 13_ 
_do_ 
Field. 
7 
4 
Do. 
Do_ 
_do_ .. 
_do.®_ 
9 
0 
Do. 
Aug. 16_ 
_do. . . 
Greenhouse 
6 
4 
Do 
Do_ 
_do.. _ 
_do.®_ 
4 
0 
Do. 
Do_ 
_do. _ 
Field. 
g 
6 
Do. 
Do_ 
_do. _ 
_do®.___ ' 
7 
0 
Do. 
Sept. 1 _ _ 
_do_ _ 
Greenhouse 
g 
5 
Sept- 19 
Do_ 
_do_ _ 
do.® 
g 
0 
Do. 
"Control. 
CROSS INOCULATIONS FROM MOSAIC CUCUMBER PLANTS TO THE MILKWEED 
The identity of the mosaic disease of the milkweed with that 
occurring on the cucurbits has also been shown by the results of 
inoculations from mosaic cucumber plants to healthy milkweeds. 
These inoculations have been relatively limited in number, but 
the results have been so definite as to amply demonstrate the pos¬ 
sibility of such infection. 
During the summer of 1920 cages were placed over four healthy 
milkweed plants, and aphids from a mosaic cucumber plant were 
colonized on each of them! Aphids from healthy cucumber plants 
were placed on four other healthy milkweeds as controls. These 
inoculations were made on August 12, and on September 1 the inocu¬ 
lated plants were found to show a curling and mottling of the leaves 
similar to the symptoms of mosaic milkweeds in the field. The 
* controls, however, also showed a less severe curling of the leaves, 
although there was no change in color. In order to make sure 
that the apparent mosaic symptoms were not merely aphis injury, 
the aphids were removed from both the inoculated and control 
plants on September 4. The plants were then allowed to remain 
until September 29, when they were again examined. On this date 
the new growth of the inoculated plants showed evident symptoms 
of mosaic, while the later growth of the control plants was normal 
in character. The presence of mosaic was proved in the case of 
the inoculated plants by the transference of aphids from these 
plants to healthy cucumbers. Between September 2 and Sep¬ 
tember 4, aphids from all the inoculated and control plants were 
transferred to healthy cucumbers under separate cages in the green¬ 
house. As shown in Table XI, the aphids from all of the inoculated 
milkweeds produced mosaic on the cucumbers, while the plants to 
which the aphids from control milkweeds were transferred remained 
normal. The success of these inoculations was further demon¬ 
strated by experiments herein described, in which the roots of these 
inoculated plants were grown in the greenhouse (pi. 2, B, C). 
Further successful cross inoculations from mosaic cucumbers to 
the milkweed were made in experiments in the greenhouse during 
1920-21. Five healthy milkweeds, grown from roots brought in 
