144 DISEASES OF GLASSHOUSE PLANTS 
suffering from mosaic disease are frequently abnormal, 
cohesion and twisting of the various parts being fairly 
common. The anthers are sometimes quite small and 
sterile, and many flowers drop from the pedicels at an 
early stage. Some workers claim that the fruits are 
frequently mottled, but this symptom has not proved to 
be common in this country. The stems are often marked 
with streaks of a paler colour, and occasionally small, 
thin, brown streaks are present. 
The total effect on the plant of all these abnormalities 
is to reduce the weight and quality of fruit produced. — 
Plants physiologically weak are more severely attacked 
than those more robust, but in commercial nurseries 
the worst results are seen after the plants have been 
‘“‘ stopped.” “Stopping” consists in cutting away the 
growing point of the main stem just above the leaf above 
the fifth truss, in order to encourage the fruit to mature. 
Side shoots are then allowed to develop and produce what 
are known as the “tops.” If an exceptionally heavy 
crop has been produced by the lower five trusses the 
“tops”? may grow away weak and spindly, and if in- 
fected with mosaic disease at that stage the effect is 
extremely bad. Mottling, distortion, and desiccation 
of the leaves follow rapidly and the yield becomes 
negligible. 
Symptoms of Cucumber Mosaic Disease 
Mosaic disease of the cucumber may easily be recog- 
nized, and two types have been observed in this country. 
One resembles the aucuba type of the potato and tomato, 
and is marked by localized yellow patches of distinct 
outline. Curling and distortion of the foliage is rare in 
this type, which apparently does little damage to the plant. 
The second type is characterized by mottling, wrinkling, 
and blistering of the leaves and dwarfing of the plant 
(Fig. 40). Infection takes place at an early stage and may 
lead to complete “‘ blindness’ of the growing point. As 
