52 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
peppers were inoculated with the expressed juice of mosaic tobacco 
plants and the inoculations later made from these plants to both 
cucumber and tobacco. All of these inoculations were made by the 
artificial method in the case of tobacco, but the cucumber plants in 
some cases were also inoculated by means of aphids as in the pre¬ 
ceding experiments. The results of these experiments (Table XXII) 
indicate that cucurbit mosaic can be transmitted to tobacco through 
the pepper, and that tobacco mosaic can be transmitted in similar 
manner to the cucumber. 5 These results seem to give some support 
to the belief that the causal agencies of these diseases are identical, 
but as yet this hypothesis can not be considered as proved. 
Table XXII. — Results of cross inoculation of cucumber and tobacco plants from 
pepper plants infected with tobacco mosaic 
Date of 
inoculation 
Pepper plant 
used as inoculum 
Plant 
inoculated 
Oct. 17, 1922... 
Do_ 
3-a (mosaic). 
10 (healthy)_ 
3-a (mosaic) 
Tobacco 
...do_ 
Cucumber 
...do. 
Tobacco.. 
..do 
Do_ 
Do_ 
10 (healthy)_ 
2 -c (mosaic). 
12 (healthy)_ 
Nov. 14, 1922.. 
Do_ 
Do... 
2 -c (mosaic)_ 
Cucumber 
...do_ 
—do. 
Tobacco 
—do.. 
Do_ 
Do. 
-do——_ 
12 (healthy). 
4-d (mosaic). 
7 (healthy)_ 
Mar. 23, 1923- 
Do.. 
Do.. 
4-d (mosaic) 
Cucumber 
—do . 
Do_ 
_do_ 
Do_ 
7 (healthy)_ 
—do. 
Method of inoculation 
Number 
of plants 
inocu¬ 
lated 
Number 
of plants 
mosaic 
Date 
observed 
Artificial___ 
Control..__ 
Aphids from mosaic 
pepper plant. 
Aphids from healthy 
pepper plant (con¬ 
trol) . 
Artificial.. 
Control_ 
Artificial__ 
Aphids from mosaic 
pepper plant. 
Aphids from healthy 
pepper plant (con¬ 
trol). 
Artificial.. 
Control_ 
Artificial.. 
Aphids from mosaic 
pepper plant. 
Aphids from healthy 
pepper plant (con¬ 
trol). 
8 
8 
8 
8 
6 Oct. 26,1922 
0 Do. 
5 DO. 
0 Do. 
8 
8 
8 
8 
8 
5 
0 
5 
8 
0 
Nov. 22,1922 
Do. 
Nov. 20,1922 
Do. 
Do. 
8 
8 
10 
10 
10 
6 
0 
6 
8 
0 
Mar. 31,1923 
Do. 
Mar. 30,1923 
Do. 
Do. 
Cross-Inoculation Experiments with the Pigweed 
, CROSS INOCULATION FROM MOSAIC PIGWEED TO THE CUCUMBER 
Field observations at Madison during the summer of 1920 showed 
that pigweeds (Amaranthus retrojlexus) which were growing near 
mosaic cucumbers were affected with a mosaiclike disease. The 
affected plants were dwarfed, the leaves were irregular in shape, 
and the younger leaves were mottled in a manner typical of the mosaic 
diseases. An examination also showed that these plants were 
infested with aphids, which were also abundant on the nearby 
mosaic cucumber plants. Aphids from the supposedly mosaic 
pigweed were transferred to healthy cucumber plants under cages 
in the greenhouse, and mosaic symptoms later developed on the 
majority of these plants. Control plants with aphids from healthy 
pigweeds, however, remained free from mosaic. In order to elimi¬ 
nate the possibility that some of the aphids on the 'pigweed had 
recently come from mosaic cucumber plants and were carrying 
8 Since these experiments were undertaken. O. H. Elmer, of the Iowa Agricultural Experiment Station, 
has reported that he has secured infection in tobacco plants directly inoculated with cucurbit mosaic. (IS) 
