8 
Journal of Agricultural Research 
Vol XXXI, No. 1 
Trials with Seed from Mosaic Plants of Wild Cucumber 
The methods followed in the experiments with seed from mosaic 
plants of Micrampelis lobata were approximately the same in all 
trials. The seed was collected from plants which showed definite 
mosaic symptoms and, in most instances, was obtained from points 
where mosaic-diseased plants had appeared during previous seasons. 
Seed was also collected from healthy plants to serve as controls. 
The seeds were dried at room temperature and then stratified 
in moist sand and held for a time at low temperatures. In the 
earlier work with the wild cucumber, considerable difficulty was 
encountered in obtaining germination of the seed, until, as a result 
of numerous experiments carried out by G. H. Harrington, formerly 
of the seed laboratory of the United States Department of Agri¬ 
culture, it was definitely shown that a period of chilling is essential 
to its germination. In the trials of 1919 the seeds were stratified 
in a box of moist sand and allowed to remain out of doors during 
the winter, being brought in and planted on April 9. In the later 
trials the seeds were, in some cases, treated in the same way, but 
most of them were packed in moist sand and placed in the ice com¬ 
partment of a refrigerator. Under these conditions, a period of 
three to five weeks was necessary for germination. A few seeds 
were tested for germination at room temperature at intervals of 
10 days, but it was found that the seed remaining on ice would 
germinate as rapidly as the test samples removed to higher temper¬ 
atures. When germination began, all the seeds were removed from 
the ice compartment and placed in moist chambers to germinate. 
Seeds which did not germinate within five days were again packed 
in sand and subjected to further chilling. Practically all the seeds 
which eventually germinated, however, did so within three to five 
days after germination was first noted, regardless of the temperature 
at which they were subsequently held. Little germination occurred 
in any of the remaining seed, although they were often kept at low 
temperature for six weeks thereafter. 
In all trials of the seeds from mosaic Micrampelis plants, the 
average percentage of germination was much lower than that of the 
healthy control seeds which had been collected at the same time and 
kept under the same conditions. The mosaic seeds had an average 
germination of 32 per cent as compared with 67 per cent in the case 
of seed from healthy plants. After germination the seeds were 
planted in 10-inch pots of sterilized soil and the plants were grown in 
a greenhouse which was isolated from those in which mosaic 
cucumbers were present. All mosaic plants in the other houses were 
kept under cages in order to avoid the danger of insect transmission 
of the disease. No aphids or striped cucumber beetles were found 
on the Micrampelis plants during any of the trials, and the houses 
were fumigated at intervals of 10 days to guard against their presence. 
The results of the trials are given in Table I. 
It will be noted that in all the trials a certain number of the 
seedlings grown from seeds of mosaic wild cucumber plants developed 
the mosaic disease, while none of the control plants showed signs of 
it at any time. All of the mosaic plants showed symptoms of the 
disease soon after the seed germinated. In every case the symptoms 
were noticeable in the first leaf, and plants which did not show signs 
