The Primitive Flower

My grandfather—my father’s father—was a mechanical engineer and he would have very much liked one of his grandsons to have followed in his footsteps (as neither of us sons had), so he tended to give my brother and me books on science. Time Life had a “nature” series and a “science” series. We got the complete science series from our grandfather in a custom-made wooden case. The nature series on the other hand, we got, I think, from our mother’s mother, and I don’t think we ever had the complete set. Both my brother and I, however, spent a lot more time going through the nature books than the science books, and neither of us became engineers.

Rudolph Zallinger's mural. Note the magnolia at left.

Rudolph Zallinger’s mural. Note the magnolia at left.

They reproduced images of dinosaurs in one of the Time Life nature volumes. Like most kids, my brother and I were crazy about dinosaurs, memorizing their names, drawing them, playing with plastic ones, and arguing over which dinosaur could beat up which. The images in the Time Life book were taken from Rudolph Zallingers “Age of Reptiles” mural, which is still on display at the Yale Peabody Museum of Natural History. One startling detail has stuck with me through all these years: the appearance of a magnolia tree right next to the Tyrannosaurus rex in the Cretaceous Period portion of the mural. All the other plants were (at the time) unfamiliar to me, but there were plenty of magnolias on Long Island.

The "cone-like" fruit of the magnolia.

The “cone-like” fruit of the magnolia.

When I took plant systematics as a graduate student we learned the structure of flowers in great detail, as they are vital to classifying plants. Magnolias have very primitive flowers, with parts that are less differentiated from the leaves they evolved from than one finds in more derived flowers. What appear to be petals on a magnolia are in fact “tepals“; they have not differentiated into petals and sepals. In addition, the cone-shaped fruit develops from a receptacle at the center of the flower marked by a spiral arrangement of stamens and carpels. The flowers are also perfect; they retain male and female organs. According to Cronquist’s Evolution and Classification of Flowering Plants (1988), the textbook that I used in grad school, the Magnoliidae subclass includes the most primitive living families: the water-lily family (Nymphaeaceae), buttercup family (Ranunculaceae) and magnolia family (Magnoliaceae).

Hence Zallingers inclusion of the magnolia tree in his dinosaur mural. The basal position of magnolias among the flowering plants, i.e. the angiosperms, was originally due to the arrangement of the carpels into a cone-like structure that resembled gymnosperm cones (i.e. pines). But it has since been shown that they are not actually homologous structures.

Magnolia grandiflora of the southeastern U.S.

Magnolia grandiflora of the southeastern U.S.

The ancient pedigree of the magnolia is also attested to by the fact that it is beetle-pollinated, rather than bee-pollinated, presumably because bees evolved after magnolias did. As bees gather pollen from flowers, the latter must have evolved before the former. Early flowering plants, then, had to be pollinated by either the wind or animals other than bees.

The genus Magnolia has only been found in fossil form back to 20 million years ago, the Miocene Epoch, well after the dinosaurs went extinct. But fossils of extinct members of the Magnoliaceae family has been found in rocks 95 million years old, or the early part of the Late Cretaceous Period. While fossils have been found in North America, Europe, and Asia, there are no modern magnolia species in Europe or the western part of Asia. Today native species are found only in southern China and in the southeast United States.

 

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