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Table 27
Table 28
Carduus lIU1tl1lS L. . 123
thistle size has declined more than its density. For example at Aylesbury. the density of
the thistle in 1982 was 97% less than in 1969. but the number of heads had declined by
nearly 99%.
Regression equations of the effect of R. con;cus Froel. on C. nUiallS L.
1. Average no. heads/plant at Aylesbury
and Findlater
2. Average head diameter at Aylesbury
3. Average head diameter at Findlater
x = no. years r = correlation coefficient
dJ.
= 994.5 - 0.50 x 26
= 79.8 - 0.40 x 12
7.3 - 2.89 x 13
r
-0.79
-0.71
-0.38
p