78 MR. DARWIN ON THE EXISTENCE OF TWO FORMS 
by insects. When insects are the agents of fertilization (and this 
is incomparably the more frequent case both with plants having 
separated sexes and with hermaphrodites), the wind plays no part, 
but we see an endless number of adaptations to ensure the safe 
transport of the pollen by the living workers. We can recognize 
these adaptations most easily in irregular flowers ; but they do not 
the less occur in perfectly regular flowers, of which those of Linum 
offer an instance, as I will almost immediately endeavour to show. 
I have already alluded to the rotation of each separate stigma in 
the long-styled form alone of Linum perenne. Inthe other species 
examined by me, and in both forms when the species are dimor- 
phic, the stigmatic surfaces face the centre of the flower, and the 
furrowed backs of the stigmas, to which the styles are attached, face 
the circumference. This is the case, in the bud, with the stigmas of 
the long-styled flowers of L. perenne. But by the time the flower 
in this form has expanded, the five stigmas, by the torsion of that 
part of the style which lies beneath the stigma, twist round and 
face the circumference. I should state that the five stigmas do 
not always perfectly turn round, two or three often facing only 
obliquely towards the circumference. My observations were made 
during October ; and it is not improbable that earlier in the season 
the torsion would have been more perfect ; for after two or three 
cold and wet days the movement was very incomplete. The flowers 
should be examined shortly after their expansion ; for their dura- 
tion is brief, and, as soon as they begin to wither, the styles be- 
come spirally twisted together, and the original position of the 
parts is lost. 
He who will compare the structure of the whole flower in both 
forms of L. perenne and grandiflorum, and, I may add, of L. flavum, 
will, I think, entertain no doubt about the meaning of this torsion 
of the styles in the one form alone of L. perenne, as well as the 
meaning of the divergence of the stigmas in the short-styled forms 
of all three species. It is absolutely necessary, as we now know, 
that insects should reciprocally carry pollen from the flowers of 
the one form to those of the other. Insects are attracted by five 
drops of nectar, secreted exteriorly at the base of the stamens, so 
that to reach these drops they must insert their proboscides outside 
the ring of broad filaments, between them and the petals. In the 
short-styled form of the above three species, the stigmas face the 
axis of the flower; and had the styles retained their original up- 
right and central position, not only would the stigmas have pre- 
sented their backs to insects ag they sucked the flowers, but they 
