Geology Reference
In-Depth Information
selves—fragmentary remains of club mosses and other suspected relatives of modern vas-
cularplants(thosewithaninternalplumbingsystemofwater-filledtubes).Lackingextens-
ive root systems, these short, stubby plants would have been restricted to low-lying, wet
areas.
The fossil record improves with time, as early plants became more widespread and ro-
bust. By four hundred million years ago, primitive vascular plants had begun to colonize
once-barren lands across the globe. They appeared as spindly, leafless, miniature shrubs
with greenish, sun-seeking photosynthetic stems and branches that rose just a few inches
abovetheground.Theirrootsefficientlypenetratedtherockygroundandprovidedasturdy
anchor, while capillary action distributed water upward.
In spite of their obvious importance to life's colonization of the land, fossilized plants
have long played second fiddle to trilobites and dinosaurs. Animals have more dynamic
lifestyles as predators and prey, and they seem more varied in form and behavior—more
like us. What's more, fossil plants tend to be fragmentary—typically an isolated leaf or
stem, a piece of bark or diagnostically patterned wood. Plants lack what University of Ch-
icagopaleobotanist KevinBoycecalls “thesatisfying completeness ofclams,” buttheytell
amazing stories nonetheless.
I first met Kevin in 2000, when he was an enthusiastic and creative graduate student at
Harvard, working with Andy Knoll and thinking about new ways to tease out those stories
from some of Earth's oldest fossil plants. A voracious reader and gifted writer, Kevin has
a knack for telling stories—he's the kind of scientist who can make the history of plants
captivating. But to tell new stories about Earth's oldest plants, Kevin needed new kinds of
data about plant fossils. Andy sent Kevin to the Geophysical Laboratory to learn about mi-
croanalytical techniques for elements, isotopes, and molecules—techniques never before
applied systematically to fossilized plants.
Our first joint research venture focused on remarkably preserved plant fossils from
the four-hundred-million-year-old Rhynie chert of Aberdeenshire, Scotland. The fortunate
Rhynie vegetation was saved from rotting when hot springs surrounded their tissues with
mineral-rich waters, hermetically sealing and partially replacing buried plant matter with
fine-grained silica. A century ago geologists discovered boulders of the chert in a stone
fence in the small village of Rhynie. Only after considerable excavation was a small tract
of actual bedrock found and quarried. Rhynie chert specimens remain precious and quite
difficult to come by, but Kevin Boyce had access to an old Harvard collection of fist-size
specimensandthin,glass-mounted,two-by-three-inchtransparentpolishedrocksectionsin
which plant anatomy down to cellular details can be studied in a microscope. These fossils
reveal fragments of a bizarre landscape, at once familiar and profoundly alien, covered in
stalklike branching plants, each with green photosynthetic stems but no leaves.
