On the Species of the Genus Primula in Essex. 165
all of their capsules, so that I had difficulty in getting un-
opened capsules, and those I did get seemed to be small,
late, and weakly ones. Unfortunately, before I had an
opportunity of counting their seeds the capsules of all but
four s. and five 1. burst, mixing the seed so that I was only
able to include them in the total weight of seeds.
It will be seen from Table IX. that these results are not
nearly so satisfactory as in the last species. The long-styled
plants in this case certainly produced rather more seeds than
the short-styled plants ; but how to account for this I do not
know, as I am convinced from my own experiments and Mr.
Darwin's that the s. do, as a rule, produce the most seed, at
least in the Primrose and Cowslip, and it is not likely that
the opposite holds good with the Oxlip. However, all the
capsules were taken from small and rather late plants, which
are, I believe, not so likely to be trustworthy; and the small
number of seeds actually counted, on account of the bursting
of the capsules, is far from satisfactory. I shall recur to this
matter at another time. Unfortunately I took no account of
the flowers which set no seed, or the result would certainly have
been different. The four highest numbers for the s. are 58, 59,
64, and 75; and the four highest numbers for the 1. are 49, 54,
54, and 57, the highest of the latter (57) being less by one
than the lowest of the former; whilst the four lowest numbers
for the s. are 3, 4, 4, and 5; and the four lowest numbers for
the 1. are 1,1,2, and 2, the highest of the latter being less by
one than the lowest of the former; so that by this standard
of comparison the s. have the advantage.22
22 I must beg leave to differ from Mr. Darwin in one statement which
he makes (p. 20), namely, that the fairest standard by which to estimate
the relative fertility of the two forms is by the product of an equal number
of umbels. Now it is certain that with a species like P. farinosa, which
rarely produces more than one umbel, this would be the case; but with
the other species of Primula (which produce an uncertain number of
umbels) we can by this standard only estimate the fertility of the umbels,
not of the plants themselves (which is what we want to get at), unless we
take account of the number of umbels which each plant produces. The
last table is a case in point; the s. umbels are the most fertile in the pro-
portion of 4 to 3, but the 1. produce almost half as many more umbels than
the s.; so that the 1. plants produce on the whole rather the most seeds.