xc
Journal of Proceedings.
It sometimes happens in the King-cup that there is more than one
sub-terminal flower, each on a simple pedicel. It is easy to imagine the
number of such flowers increased indefinitely. This conception is
realized in the genus Aconitum. The lower branches of the stem in
Aconitum paniculatum retain their terminal flowers and have also flowers
at their sides, thus forming a real panicle. The main axis of the stem
is not, I think, so constant either in the possession of or in the want of a
terminal flower. In the common Monkshood (Aconitum napellus), neither
the main axis nor any branch of the flowering stem is terminated by a
flower, but sometimes even A. napellus reveals its affinity with plants
having definite inflorescence by a pair of minute bracts on the stalk
which bears a flower. This phenomenon is not, however, constant, nor
perhaps frequent, but may be observed sometimes.
If we regard the King-cup (Caltha palustris) as representing the
primary form of inflorescence from which other forms may have been
evolved, it is interesting, in view of some recent speculations on the
evolution of colour in flowers, to find the flowers of Caltha yellow and
without petals, those of Aconitum paniculatum variegated with blue and
white, while those of the Monkshood (A, napellus) are in an indefinite
raceme, and of the deepest blue. Ranunculus differs from Caltha, and
resembles Aquilegia in that the uppermost branch below the summit of
the main axis is not a simple pedicel bearing a solitary flower, but a
peduncle capable of branching and often actually giving origin to a lateral
flower besides that upon its top ; so that we find flowers on the primary,
secondary, and tertiary axes, as in those plants which have a truly
centrifugal inflorescence. Indeed, if the two uppermost branches of
Ranunculus acris (the tallest Buttercup, which gives a yellow brilliance
to fields where grass is growing to be cut for hay) were opposite, the
order of expansion among the flowers of this plant would be really centri-
fugal, for the branches below these two are considerably behind them
in the expansion of their flowers; but it sometimes happens that the
uppermost branch but one expands its flower before that which is between
it and the summit. This is the nearest approach to a centrifugal order
of expansion without reaching it, or perhaps I should say without con-
stantly maintaining it, that I know of.
Thus we see a gradation from the diffuse but definite mode of inflores-
cence observed in Caltha palustris, through the panicle of Aconitum
paniculatum, to the indefinite spike or raceme of Aconitum napellus. On
the other hand we see Ranunculus acris and other species of Ranunculus
bearing considerable resemblance to Caltha, but with so much difference
as to approach the centrifugal habit of Silene.
In the same natural order as the plants that we have been considering
is the Traveller's-joy (Clematis vitalba), whose flowers are disposed in a
manner so regular that we might regard it as the typical form of
inflorescence with which other forms might be compared. In this plant
the flowers are in a panicle, sometimes with a flower at the end of the
main axis, which is however not often produced till near the end of the
summer, when the flowers on axillary peduncles have given place to
clusters of achenes with feathery tails. The leaves of this plant being
opposite, so are the peduncles in their axils. The bracts which these
peduncles bear are opposite as well, and each of them has a flower-stalk
in its axil. So each axillary peduncle is the basis of a panicle, the
flowers of which are arranged on the same plan which prevails through-
out the entire flowering system. It is often not upon the top of a panicle
that the first flower expands, but on one of the lower branches; then the
flowering proceeds upwards as concerns the branches, but the terminal
flower will be open before that of the uppermost branch. Clematis vitalba
differs from Caltha palustris not only in its flowering branches being