474 BOTANICAL GAZETTE [UNE 
part of the field about 5 per cent of the Physalis plants showed 
mosaic. The reciprocal cross inoculations proved that the causal 
viruses were identical. Physalis was generally distributed in this 
vicinity, and a survey showed that mosaic did not occur to any 
extent on the plants at a distance from the tomato field. In acorn 
field about 40 rods distant, several hundred Physalis plants were 
examined and only two showed mosaic. Horse nettle was present 
in the tomato field, but showed no mosaic symptoms. 
The location of a number of the mosaic Physalis plants in the 
tomato field was carefully noted. The following year this field was 
planted in corn and no tomatoes were grown in the neighborhood. 
On July 15, 1920, an inspection of the field showed the Physalis 
plants again abundant, and in the same part of the field where 
mosaic was noted in 1919 the disease was now conspicuous on a 
much higher percentage of the plants than had been observed the 
preceding fall. In a corn field adjacent to the west side of the 
experimental field, mosaic was found among the Physalis plants 
along the edge, but not over 100 feet distant from the fence. In 
another corn field near the east side of the experimental field, mosaic 
was also found on many of the P/ysalis plants. Since no tomatoes 
were being grown in the vicinity this season, the prevalence of 
mosaic on Physalis at this early date indicated that the disease 
must have persisted in the weeds over winter. The greater preva- 
lence of the disease as compared with the preceding September 
may possibly be explained by the fact that many of the weeds had 
not shown definite mosaic symptoms in the fall, whereas the young 
shoots of the following spring showed conspicuous symptoms. It 
has been noted that mosaic symptoms on old plants in the fall may 
become very inconspicuous. 
OVERWINTERING OF VIRUS IN ROOTSTOCKS 
Physalis subglabrata is perennial by means of a thick rootstock 
12~18 inches below the surface of the soil, deep enough to escape 
harm from ordinary cultivation practices. In the fall of 1919 
some of these rootstocks of mosaic plants were dug, and an 
unsuccessful attempt was made to carry them over winter in pots 
of soil. The test was repeated the next year. Late in August 
