This diagram shows how the evolution of plants families as we understand them today matches the physical layout of the new Family beds at the National
Botanic Gardens.
On the far left are the MONOCOTS, which have all their flower parts in threes or multiples of threes. The first families, like the flowering rush, Butomus
have many separate ovaries, as you progress along these beds, the ovaries of the flowers become fused into a single compound ovary, the anthers become reduced in
number to 3 (Iris family) or 1 (Orchids and Gingers), and floral parts become reduced and minute (Grasses & Sedges).
Buttercups and Poppies are the most primitive of all the other evolutionary lines, unlike the Monocots, Paleotrees and Paleoherbs they have pollen grains
with 3-pores as opposed to just a single pore. Plane trees and Proteas are closely related, and evolved from the buttercups at an early point in evolution.
A number of other early offshoots of the Buttercup lineage are the CARYOPHYLLIDS (Pinks, Catchflies and Docks) and SAXIFRAGALES (Saxifrages,
Sedums and Paeonieas).
The ROSIDS have separate petals that can be pulled off the flower one at a time. The initial beds, with the Cabbages and Violets have separate stamens
also, while in families like the Mallows the anthers are fused into bundles. The Geraniums, Impatiens and Oxalis have their stamens fused to the base of
the flower. The Peas, Roses and Passionflowers have the stamens fused to the Calyx. As you progress through these beds the number of flower parts
reduces, and the ovaries move from being above the flower in Buttercups, to being completely hidden and below the flower in Fuchsias and the Carrot family.
The ASTERIDS have their petals fused together, making a tubular flower. The Daisy family and Campanulas have ovaries that lie below the flower, while in
the Heather family onwards, the ovaries are contained inside the corolla tube. The Heather and Primrose families are characterised by having twice as many
anthers as petals. From the corner bed onwards all the flowers have an ovary with just two compartments. Families like the mints at the very end of these
beds have the fewest number of floral parts, with just 2 or 4 anthers per flower. These flowers are very specialised and efficient at being cross pollinated.
Visiting the Gardens
Order beds or Family beds have been part of Botanic Gardens almost since their inception. They provide a means to display the systematic
arrangement and relationships of plants to one another. Before an understanding of evolution, this was either based upon a folk-taxonomy of
growth forms (trees, shrubs, and herbs for example) or more practical divisions, such as medicinal usages or geographical origins.
1. PALEOTREES: Some of the earliest fossils of flowering plants are virtually indisitinguishable from modern Magnolia flowers. It is a remarkable fact that
the pollinators of Magnolia flowers today (Beetles) were the only flying insect group at the time (bees and butterflies evolved much later), so it seems that the
flowers of these trees have retained the same structure, and the same pollinators for over 100 million years !
2. PALEOHERBS: The ancient position of the water lilies has long been overlooked. Other paleoherbs are characterised by their unusual
flowers (Aristolochia) aromatic oils (Pepper family, Illicium) and flowers with many petals and sepals that intergrade with one another (Schisandra).
3. MONOCOTS: Paleotrees, Paleoherbs and Monocots all share the characteristic of pollen grains with a single pore or groove, through
which the pollen tube germinates. The other defining characteristics of the Monocots are the floral parts in threes, and the single cotyledon of the seed.
4. EUDICOTS (Including the ROSIDS & ASTERIDS):
The remaining lineage is the true dicots (Eu- = true). All Eudicots have 3-porate pollen, while the Paleo groups and
Monocots all share monocolpate pollen. One of the more unexpected discoveries was
that the Sacred Lotus (Nelumbo) was closely related to the Proteas and the Plane tree, and that these three, seemingly unrelated families, are
closely related, and diverge from the earliest Buttercup-like groupings.
21 RANUNCULACEAE
29 LINACEAE
35/36 LEGUMINOSAE
11 CARYOPHYLLACEAE
16 SAXIFRAGACEAE
50 CAPRIFOLIACEAE
56 ERICACEAE
61 OLEACEAE
