Boraginaceae - Borage family
Above: Viper's-bugloss, Echium vulgare. The inflorescence is a spike with
scorpioid cyme side-branches. Cymes are sympodial branching units and
scorpioid means that the flowers are borne on the axis on alternating sides.
The proximal flowers (those nearest the main spike axis) open first and the
others follow in succession. The flowers are pink initially but turn blue as they
open and mature. The bract accompanying each flower bud is clearly visible on
each cyme. There is a slight asymmetry to the flower, with the stamen filaments
arching upwards (adaxially). The floral formula is: K(5) C(5) A(5)
G(2) with each
of the two fused carpels divided into two, resulting in a four-chambered ovary.

These plants occur on sandy and chalky soils, such as chalk grasslands, sand
dunes, cliffs and disturbed ground. The large showy flower spikes attract bees
and butterflies to pollinate the plant. This plant has been the subject of much
analysis in an attempt to answer questions like: How do pollinators divide their
time between the flowers on one spike? What is the optimum number of flowers
per spike? How does having more flowers trade off against the risks/benefits of
geitonogamy (fertilisation of a flower on a spike by pollen from another flower of
the same spike)? These questions are important if we are to understand why
some plants have large showy flower spikes with many flowers whilst others
have only solitary flowers.

Viper's-bugloss is either biennial or a
semelparous (monocarpic) perennial
meaning that it reproduces then dies. Setting flowers is not enough to bring
about death of the plant, rather it must set seed. This contrasts with iteroparous
(polycarpic) perennial plants which can set seed each year.

The
nectary is a rounded octagonal disc surrounding the base of the ovary
with about 200 to 600 stomata through which the nectar is presumably
secreted. The style is covered in long, dense and non-glandular trichomes,
whilst the stigma is covered in unicellular papillae (see
trichomes) which have
stalks expanding into a 'corrugated umbrella'. The corrugations of neighbouring
papillae interlock, especially in young flowers. The outer (lower or abaxial)
surface of the calyx (fused sepals) bears many non-glandular trichomes formed
of one to several cells and up to about 1.4 mm in length and fewer much
shorter glandular hairs, each consisting of a stalk with a spherical head formed
by a single cell. The function of these structures is presumably to guard the
flower against nectar and pollen-stealing insects which do not affect pollination.
However, it should be remembered that pointed non-glandular trichomes have
been shown to have a sensory function in some plants - detecting walking
insects by touch and mobilising the plant's chemical defences in response. It
would be interesting to see whether or not the non-glandular calyx trichomes of
Echium are tactile sensors. (See the beautiful study by:
Weryszko-Chmielewska, E. and M. Chwil, 2008. Micromorphology of glandular
structures in
Echium vulgare L. flowers. Acta Agrobotanica 61: 25-34. This
study is available online.)
Myosotis sylvatica


Article updated:

9 June 2015
24 July 2016
Above: Forget-Me-Nots, Myosotis, like this Wood Forget-Me-Not (Myosotis
sylvatica
) with their unmistakable small blue flowers are also members of the
borage family.