38 
Journal of Agricultural Research 
Vol. XXXI, No. 1 
Table XIV .—Results of cross inoculations from mosaic cucumber to healthy 
pokeweed plants by means of aphids 
Date of inocu¬ 
lation, 1922 
Method of inoculation 
Mar. 15. 
Apr. 6.. 
Do. 
Apr. 17. 
Do 
May 8_. 
Do. 
July 16. 
Do. 
July 29. 
Aug. 3__ 
Do. 
Do. 
Aphids from mosaic cucumber plant_ 
_do..___ 
Aphids from healthy cucumber plant (control).. 
Aphids from mosaic cucumber plant.. 
Aphids from healthy cucumber plant (control) __ 
Aphids from mosaic cucumber plant__ 
Aphids from healthy cucumber plant (control).. 
Aphids from mosaic cucumber plant_ 
Aphids from healthy cucumber plant (control).. 
Aphids from mosaic cucumber plant_ 
_do____ 
_do______ 
Aphids from healthy cucumber plant (control).. 
Number 
of aphids 
per plant 
Number 
of plants 
inocu¬ 
lated 
V 
Number 
of plants 
mosaic 
Date ob¬ 
served, 
1922 
16 
3 
0 
Apr. 
15 
6 
5 
Apr. 14 
15 
2 
0 
Do. 
15 
4 
0 
May 8 
15 
2 
0 
Do. 
25 
8 
5 
May 17 
25 
4 
0 
Do. 
25 
4 
1 
July 25 
25 
2 
0 
Do. 
30 
12 
8 
Aug. 7 
30 
12 
6 
Aug. 11 
(°) 
3 
2 
Aug. 9 
25 
12 
0 
Do. 
° Aphids transferred naturally from mosaic cucumber plant in same cage. 
place by a clamp, the screen on the under leaf surface preventing 
crushing by the clamp. This method proved successful, but after a 
time it was found that if a large number of aphids were colonized on 
the plants a few would remain without being confined in any way. 
It Was also noted that the offspring of the aphids which remained on 
the pokeweed would feed more readily on this host than did the 
parent insects. The use of cages was therefore abandoned as unneces¬ 
sary. It was later found that aphids would colonize readily on the 
pokeweed in large numbers during the spring and summer, possibly 
on account of some change in the juices of the pokeweed owing to 
its more vigorous and succulent growth. 
The results of the inoculations by means of aphids were not as 
consistent with the pokeweed as with some other hosts, owing to the 
earlier difficulty in the colonization of the insects on the plants. The 
evidence, however, shows that the mosaic disease of cucurbits may 
be readily transmitted to the pokeweed. 
TRANSMISSION OF MOSAIC FROM THE POKEWEED TO THE CUCURBITS 
Reciprocal inoculations have also been made from mosaic poke- 
weed plants to the cucumber and muskmelon. In these inoculations 
the writers were again able to produce infection when aphids were 
used as a means of inoculation out were unsuccessful in producing 
infection by artificial inoculations. The results, as shown in Table 
XV, indicate that both the muskmelon and cucumber are susceptible 
to pokeweed mosaic (pi. 4, B). This being the case, it is evident 
that the pokeweed represents another perennial wild host of cucurbit 
mosaic. 
OVERWINTERING OF CUCURBIT MOSAIC ON THE POKEWEED 
Trials with Roots of Mosaic Plants 
Since the pokeweed is a perennial and is known to be susceptible 
to cucurbit mosaic, it would be expected that the disease would live 
over winter in the roots of infected plants. Field observations in 
Michigan during 1915, 1916, and 1923, and at Anna, Ill., during 1922 
and 1923, have shown that the roots of mosaic plants will again 
