Pod I, 13 seeds.
II, 14 "
III, 11 "
IV, 11 "
V, 10 "
VI, 12 "
VII, 16 "
VIII, 12 "
IX, 8 "
X, 14 "
XI, 17 "
XII, 18 "
XIII, 17 "
XIV, 15 "
XV, 14 "
————
Total XV, 202 seeds,
or 13.4 per pod.
From this it will be seen that the minimum number of seeds found was
8, the maximum 18, with an average of 13.4. Since the pods were simply
gathered at random, there is no certainty of gaining the maximum or
minimum number of seeds, but a fair average of the number produced
may be expected. September 4 three plants were examined to determine
something about the range of variation in the number of ovules produced
in the pods of a single plant. The results are given as follows:
Plant 1 varies from 5 to 11.
Plant 2 varies from 8 to 18.
Plant 3 varies from 9 to 14.
Plant 1 had 35 pods, plant 2 had 64, and plant 3 had 27.
Plant 1 was selected on account of the small
number of seeds produced per pod.
It will be seen from table D that an average of nearly 3.3 flower
buds per cluster is produced. These were moderate-sized, healthy
plants, producing on the whole probably more than the average number
of clusters per plant. On the ten plants, there were produced 342
clusters, which bore 344 seed pods, instead of about 1120, the number
of flowers which might be expected, thus giving less than thirty-three
per cent. of the buds which produce mature seed pods.
It will be seen that, while in the observations made on _S. rostratum_
the flowers which failed to produce seed did not reach much over six
per cent., in _C. chamæcrista_ it is over sixty per cent. In addition
to this fact, it is rare to see a seed pod of _S. rostratum_ which has
been destroyed by insects or other destructive agencies, while in 460
pods of _C. chamæcrista_ which were examined at Lake View, September 4,
not one was found which did not have some of the ovules destroyed by
the larvæ of some insect, and probably this would amount on the average
to fifty per cent. of all the seeds produced, being in the case of some
plants as high as seventy-five per cent.
A convenient method of approaching the question of the production of
seeds might be to determine the number of seed pods produced on a given
area of ground. A general idea may be obtained from the examination of
the plants growing upon two square feet of ground. In the first case,
the plants were much crowded; in the second, not nearly so much so; in
fact, it may be said they were growing under “normal” conditions. It
might be interesting to compare the results. The material for the two
tables was taken September 4.
FIRST SQUARE FOOT.
Plant 1, pods 0
" 2, " 10
" 3, " 4
" 4, " 13
" 5, " 0
" 6, " 12
" 7, " 3
" 8, " 1
" 9, " 4
" 10, " 3
" 11, " 0
" 12, " 25
" 13, " 2
" 14, " 0
" 15, " 0
" 16, " 10
" 17, " 2
" 18, " 0
" 19, " 0
" 20, " 0
" 21, " 0
" 22, " 6
" 23, " 1
" 24, " 5
" 25, " 2
" 26, " 3
" 27, " 0
" 28, " 3
—— ———
Total, 28, pods 109
SECOND SQUARE FOOT.
Plant 1, pods 1
" 2, " 50
" 3, " 36
" 4, " 15
" 5, " 48
" 6, " 34
" 7, " 9
" 8, " 11
" 9, " 9
" 10, " 3
" 11, " 0
" 12, " 7
—— ———
Total, 12, pods 223
In the first square foot of ground, where the plants were much crowded,
of the twenty-eight plants, ten produced no seed pods at all, and of
the remaining eighteen only six produced over five each. On these
plants an average of a little less than four pods per plant was
produced. In the second lot, where, evidently, the plants were not
nearly so crowded, only four produced fewer than five seed pods, and
there was a general average of 18.7 pods per plant.
On the first foot of ground, then, there might be produced in the
neighborhood of 1300 seeds; on the second, 2600. The large _Solanum_
upon which 40,000 seeds were estimated would probably cover an area of
12.5 square feet, giving 3200 seeds per square foot. Of course, these
figures represent only certain isolated cases, which in a way are
typical, but must not be taken to represent the average condition.
The largest plant noted September 4 had produced 100 pods, with an
average of thirteen seeds per pod; this plant might show 1300 seeds.
Professor Todd discusses in his paper the occurrence of similar
divergences from the typical form in other Solanaceæ and Leguminosæ,
and tries to discover some hint as to their origin. Lack of material
for observation precludes any present discussion of these points.
The results of these observations may be briefly summarized as follows:
Solanum rostratum.
1. As Professor Todd observed, the numbers of right-and left-handed
flowers on a plant of any considerable size are about equal.
2. As a general rule, only one flower opens at a time on a raceme,
but very commonly two will open on the raceme the same morning,
giving a right-and left-handed flower opening simultaneously, and
thus permitting in a considerable number of cases pollination between
flowers on the same raceme, even if Professor Todd’s theory of the
method of pollination be the correct one.
3. Even on the smaller branches of the plant, the flowers are almost
always approximately divided into the two types.