92
N. WALOFF
after which growth continues, but more lateral branches are p r o d u d
(see Table 11).
TABLE I1
Growth of broom in plantation no. 1, where 1623 8 d i 7 q 8 avemging
12 em in height uwe planted in March 1957
Date
Number
' examined
Average
height in c m
Limits
March 1957
July 1957
September 1957
April 1969
September 1960
May 1960
May 1901
1623
160
166
166
160
164
146
12
28
99
186
183
186
191
8-15
8-71
30-157
30-306
30-320
76-305
61-290
The measurements of the absolute amount and also of the ratio of
the green material to wood were made annually either at the end of
August or at the beginning of September from 1969 to 1966. Each year
48 qua;ters of bushes selected at random within the 1957 plantation
were cut off. The quarters were divided into the green shoots and wood
and weighed. As can be seen in Table I11 there was a progressive increase in the total weights of the bushes in the first 6 years. Much broom
was killed in the hard winter of 1961-62 and that probably accounts
for the drop in weight in 1962. There was again much growth in 1964,
but by then the ratio of the green material to wood had fallen, as had
the absolute weight (i.e. amount) of green twigs. The fall in the ratio
continued in subsequent years (see Table 111).
Whole bushcs of broom rarely die in one season, but gradually degenerate with age. In 1965 we examined 166 8g-year-old bushes selected
at random and they fell into the following 5 categories: 9.09% were
totally dead, 23.03% had only 0.25 Iiving branches, 23.03% had 0.5
living branches, 30.3% had 0.76 branches alive and 14-55°/0 of the
hushes were totally alive. Dr S. Agwu repeated these observations in
1966 and found t h a t the fractions of live bushes in the field amounted
to 841 whole bushes, out of the original 1623 planted in Area 4. Thus,
in $14 years the death rate was 48.2% of broom growth.
Similar drastic reduction in the quantity of ageing broom occurred
in another area (Richards and Waloff, 1961) where more than 75% of
old broom died before there was any detectable regeneration.
The degree to which the large insect fauna contributed to the degeneration of the host plant is still unknown. The Iarge population of
the moth Leucoptera spartifoliella Hb. the larvae of which mine the
N. WALOFF
after which growth continues, but more lateral branches are p r o d u d
(see Table 11).
TABLE I1
Growth of broom in plantation no. 1, where 1623 8 d i 7 q 8 avemging
12 em in height uwe planted in March 1957
Date
Number
' examined
Average
height in c m
Limits
March 1957
July 1957
September 1957
April 1969
September 1960
May 1960
May 1901
1623
160
166
166
160
164
146
12
28
99
186
183
186
191
8-15
8-71
30-157
30-306
30-320
76-305
61-290
The measurements of the absolute amount and also of the ratio of
the green material to wood were made annually either at the end of
August or at the beginning of September from 1969 to 1966. Each year
48 qua;ters of bushes selected at random within the 1957 plantation
were cut off. The quarters were divided into the green shoots and wood
and weighed. As can be seen in Table I11 there was a progressive increase in the total weights of the bushes in the first 6 years. Much broom
was killed in the hard winter of 1961-62 and that probably accounts
for the drop in weight in 1962. There was again much growth in 1964,
but by then the ratio of the green material to wood had fallen, as had
the absolute weight (i.e. amount) of green twigs. The fall in the ratio
continued in subsequent years (see Table 111).
Whole bushcs of broom rarely die in one season, but gradually degenerate with age. In 1965 we examined 166 8g-year-old bushes selected
at random and they fell into the following 5 categories: 9.09% were
totally dead, 23.03% had only 0.25 Iiving branches, 23.03% had 0.5
living branches, 30.3% had 0.76 branches alive and 14-55°/0 of the
hushes were totally alive. Dr S. Agwu repeated these observations in
1966 and found t h a t the fractions of live bushes in the field amounted
to 841 whole bushes, out of the original 1623 planted in Area 4. Thus,
in $14 years the death rate was 48.2% of broom growth.
Similar drastic reduction in the quantity of ageing broom occurred
in another area (Richards and Waloff, 1961) where more than 75% of
old broom died before there was any detectable regeneration.
The degree to which the large insect fauna contributed to the degeneration of the host plant is still unknown. The Iarge population of
the moth Leucoptera spartifoliella Hb. the larvae of which mine the