78 DISEASES OF GLASSHOUSE PLANTS 
plants were submitted in any one position, certain facts 
emerge which have been fully confirmed by observations 
on commercial nurseries. Chief among these are the bene- 
ficial effects which shade and temperatures above 24:0° C. 
have upon plants suffering from wilt. Table 4 (p. 77) 
shows that average temperatures of 16-6° C. and 20-0° C. 
are favourable to the rapid progress of the disease, that 
of 12-5° C. is unfavourable, while that of 25° C. practically 
inhibits it. It will be seen that the organism has travelled 
most rapidly up the stem, as indicated by the browning 
of the wood, at 16:6° C. and 20° C. and at these tempera- 
TABLE 5. 
TOMATO HOUSE. CUCUMBER HOUSE. 
SSS Frame. 7 us 
D- n- 
shaded. | Shaded. | ghadea. | Shaded. 
Date of inoculation | 14/4/20 | 14/4/20 | 14/4/20 | 14/4/20 | 14/4/20 
No of days from 
inoculation ‘Me 21 21 21 21 21 
Average tempera- 
ture ° C. ou 17 22 20 26:3 25 
Ratio of wilted to 
total leaves .. 6:10 8:10 1:10 0:10 0:10 
tures, also, complete wilt occurred most rapidly. The 
results shown in Table 5, while confirming the tempera- 
ture relations shown in the preceding table, also show the 
beneficial effect of shade. While plants in the unshaded 
house readily wilted, those in the shaded house did not 
wilt although the temperature was favourable to the 
disease. 
General observations have also shown that tempera- 
tures between 15-6° C. and 24° C., with an optimum of 
21-1°-22-8° C. are favourable to the rapid progress of 
Verticillium wilt, which below 15-6° C. and above 24° C. 
is exceedingly slow, while suitable shading counteracts 
the effects of low temperatures. 
A series of experiments were next arranged in which 
