The flowering plants or angiosperms emerged in the Cretaceous period, some 130 million years ago. Their origin Charles Darwin described as "that abominable mystery". These sporophytes dominate the landscape around us and are the most successful plant group, with something like a quarter of a million species described. Angiosperm means "contained seeds" and unlike the previous seed plants examined, the ovules are sealed within the carpel and the seeds sealed within a fruit.
People
become so obsessed with flowers it is important to remember a flower is
nothing more than a cluster of spore-bearing leaves surrounded by whorls
of protective and often albeit attractive leaves.
The flowering plants are classified into
300+ families, largely on the basis of the flower, their reproductive
organ. Imagine recognizing an organism on the basis of just its
reproductive parts! (see Schiebinger,
1996)
The Magnolia
flower (right) shows many features of the earliest flowers. (Soursop
flowers are a good local equivalent.) Spirally arranged microsporophylls
(anthers) and megasporophylls (carpels) are surrounded by
non-spore-bearing leaves (petals and sepals which together are termed the
perianth).
The earliest pollinators were just beetles chomping their way through flowers, accidentally spreading pollen and, in view of the bounty of flower parts, sparing some carpels to form seed and fruit. The insects and flowers co-evolved and flower structure and insect mouth parts have come a long way from these rather haphazard initial relationships.
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