54 BULLETIN 879, U. S. DEPARTMENT OE AGRICULTURE. 
of drastic efforts for its eradication, the disease spread gradually 
through the plat until it reached the rows adjoining the seed test, 
where it first appeared on August 8. After this date, it worked 
slowly through the plat, although all mosaic vines were removed as 
soon as noted. The plants had remained healthy for seven weeks, 
however, and the disease which appeared was so clearly a result of 
outside infection that the evidence of seed transmission may safely 
be called negative. 
Tests of 1917. — In '1917 a further trial of mosaic seed was again 
conducted at Big Rapids, Mich., using seed collected from Michigan, 
Indiana, and Wisconsin. In this work the seed from 119 fruits was 
planted on new land, located at some distance from that used in 
former experiments and on considerably higher ground. 
The plat was about 1 acre in size and was between two other blocks 
of cucurbits, principally cucumbers. No other experiments with 
mosaic were made during the season in any of the plats. About 
5,500 plants were under observation and 1,150 of these were covered 
with cheesecloth cages to prevent accidental infection by insects. 
Use was made of 250 cages, each covering from 3 to 15 plants. They 
were set out as soon as the seed was planted and were not lifted until 
late iii July, except where repairs were necessary. The writer was 
absent from Big Rapids most of the time, and the planting and early 
inspection work was done under the supervision of Mr. W. W. Gilbert. 
The plants were left unthinned as long as possible and were inspected 
at frequent intervals. The writer examined the plants, beginning 
July 30, and lifted all cages for the purpose of inspection. Great 
care was taken to avoid outside infection from insects, and the cages 
were replaced at once. A few striped beetles were present in the field, 
but only one cage was found to contain insects. All uncaged plants 
in the seed test and in the adjoining plats were free from mosaic, and 
all caged plants were healthy with a single exception. This plant 
was abnormally dwarfed, its lower leaf was yellow and wilted, and 
the four other leaves were peculiarly dark green in color and showed 
slight indications of a yellow mottling. (PL I, A.) All of the remain- 
ing plants which were in the same cage were of normal size and appear- 
ance, without the least trace of insect injury. This cage had no de- 
fects in its covering and had not been lifted after the seed was planted. 
The writer again visited the field on August 18 and inspected the 
plants. No case of mosaic was found in the plat with the exception 
of the suspected plant found on July 30. The appearance of this 
was so unmistakably mosaic that 12 healthy plants were inoculated 
from the juice of one of its leaves and covered with cages. Most of 
these developed typical mosaic symptoms on leaves and fruits, and 
there is no doubt that the plant in question was mosaic. Mr. Gilbert 
reported that no further cases of mosaic appeared on cucumbers in 
