STUDIES ON THE INSECT FAUNA ON SCOTCH BROOM
91
Parnell (1Q84a, 1964b, 1966) who studied the insect fauna within the
podrr aho studiod the pod i b l f a8 a temporary habitat. He showed that
for the same weight, of broom the crop of pods produced by the young
3-year-old bushes was greater than t h a t by the old 10 to 11-year-old
bushes, the ratio of pods being 10033. The lengths of the pods on the
young and the old bushes were the same, varying between 21 and
65 mm, with means of 38 and 40-5 mm which were not statistically
different. The commonest number of seed rudiments in pods from
bushes of all ages was 17. However, the variances of means of the
numbers of seed rudiments from bushea of two ages were significantly
different (t = 5.63, n = 1855), since there were more pods with 11-14
rudiments on old broom, more with 18-25 on young and approximately
equal numbers with 15-18 rudiments on plants of both ages. These
observations were repeatable in 2 consecutive years. As the number of
seed rudiments varied directly with the length of pods, regression equations were computed to relate t.hese two viables. The number of seeds
which matured in the pods on the old and young bushes also differed
and these differences are shown in Table I. To sum up, aa the bushes
grow older there is a reduction in the number of pods produced, in the
size of pods and also in the number of seeds per pod.
TABLE I
Number of mature seed9 in pods on young (2-3 year old) and old
(10-11 year old)) brooln bwhm at Silwood Park (Parnell 1962)
Year
Old Broom
Young Broom
No. pods
Average no.
No. pods
Average no.
examined
mature
examined
mature
seeds
seede
1959
746
6 - 1
1091
7.2
1960
1275
5.9
1275
8.2
1962,
California, age of broom not specified (Frick, 1962)
No. pods
Average no.
examined
mature eeeds
300
8-8
The progressive changes in the broom bushes were also gauged by
other means. In a plantation of known age we have measured the increase in height of the bushes from year to year as well aa the absolute
weights of green material and wood. Generally broom bushes grow to a
height of 1.8-2.4 m although n few remain smaller and some reach the
height of 3-7 m. The maximum height is usually reached in 2.5-3 years
91
Parnell (1Q84a, 1964b, 1966) who studied the insect fauna within the
podrr aho studiod the pod i b l f a8 a temporary habitat. He showed that
for the same weight, of broom the crop of pods produced by the young
3-year-old bushes was greater than t h a t by the old 10 to 11-year-old
bushes, the ratio of pods being 10033. The lengths of the pods on the
young and the old bushes were the same, varying between 21 and
65 mm, with means of 38 and 40-5 mm which were not statistically
different. The commonest number of seed rudiments in pods from
bushes of all ages was 17. However, the variances of means of the
numbers of seed rudiments from bushea of two ages were significantly
different (t = 5.63, n = 1855), since there were more pods with 11-14
rudiments on old broom, more with 18-25 on young and approximately
equal numbers with 15-18 rudiments on plants of both ages. These
observations were repeatable in 2 consecutive years. As the number of
seed rudiments varied directly with the length of pods, regression equations were computed to relate t.hese two viables. The number of seeds
which matured in the pods on the old and young bushes also differed
and these differences are shown in Table I. To sum up, aa the bushes
grow older there is a reduction in the number of pods produced, in the
size of pods and also in the number of seeds per pod.
TABLE I
Number of mature seed9 in pods on young (2-3 year old) and old
(10-11 year old)) brooln bwhm at Silwood Park (Parnell 1962)
Year
Old Broom
Young Broom
No. pods
Average no.
No. pods
Average no.
examined
mature
examined
mature
seeds
seede
1959
746
6 - 1
1091
7.2
1960
1275
5.9
1275
8.2
1962,
California, age of broom not specified (Frick, 1962)
No. pods
Average no.
examined
mature eeeds
300
8-8
The progressive changes in the broom bushes were also gauged by
other means. In a plantation of known age we have measured the increase in height of the bushes from year to year as well aa the absolute
weights of green material and wood. Generally broom bushes grow to a
height of 1.8-2.4 m although n few remain smaller and some reach the
height of 3-7 m. The maximum height is usually reached in 2.5-3 years