The Different Forms of Flowers on Plants of the Same SpeciesDarwin, Charles
Science
The Different Forms of Flowers on Plants of the Same Species
Darwin, Charles
Fertilization of plants; Heterostylism; Plant physiology; Plants -- Variation; Pollination
If we consider the results of the two legitimate unions taken together and the
two illegitimate ones, as shown in Table 1.7, we see that the former compared
with the latter yielded capsules, whether containing many seeds or only a few,
in the proportion of 77 to 45, or as 100 to 58. But the inferiority of the
illegitimate unions is here perhaps too great, for on a subsequent occasion 100
long-styled and short-styled flowers were illegitimately fertilised, and they
together yielded 53 capsules: therefore the rate of 77 to 53, or as 100 to 69,
is a fairer one than that of 100 to 58. Returning to Table 1.7, if we consider
only the good capsules, those from the two legitimate unions were to those from
the two illegitimate in number as 71 to 31, or as 100 to 44. Again, if we take
an equal number of capsules, whether good or bad, from the legitimately and
illegitimately fertilised flowers, we find that the former contained seeds by
weight compared with the latter as 50 to 24, or as 100 to 48; but if all the
poor capsules are rejected, of which many were produced by the illegitimately
fertilised flowers, the proportion is 54 to 35, or as 100 to 65. In this and all
other cases, the relative fertility of the two kinds of union can, I think, be
judged of more truly by the average number of seeds per capsule than by the
proportion of flowers which yield capsules. The two methods might have been
combined by giving the average number of seeds produced by all the flowers which
were fertilised, whether they yielded capsules or not; but I have thought that
it would be more instructive always to show separately the proportion of flowers
which produced capsules, and the average number of apparently good seeds which
the capsules contained.
Flowers legitimately fertilised set seeds under conditions which cause the
almost complete failure of illegitimately fertilised flowers. Thus in the spring
of 1862 forty flowers were fertilised at the same time in both ways. The plants
were accidentally exposed in the greenhouse to too hot a sun, and a large number
of umbels perished. Some, however, remained in moderately good health, and on
these there were twelve flowers which had been fertilised legitimately, and
eleven which had been fertilised illegitimately. The twelve legitimate unions
yielded seven fine capsules, containing on an average each 57.3 good seeds;
whilst the eleven illegitimate unions yielded only two capsules, of which one
contained 39 seeds, but so poor, that I do not suppose one would have
germinated, and the other contained 17 fairly good seeds.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account