Plants Through Time

This presentation shown here was a small part of a larger project by Hewlett-Packard for Earth Day 1997.

The setting of the Plant display was a "Walk through Time" (WTT). This was a one-mile (5,280 feet) walk, to the scale of 1 million years per foot == 5 billion years. Posters were placed approximately every 30 feet to chronicle the development of life on earth.

The WTT team plans to eventually make the text and pictures available for other groups to do their own exhibit. Our hope is that the whole world will be able to share in this understanding of our planetary journey by the year 2000.

If you'd like to do your own display, a HOWTO writeup is available.

Introduction and Overview

. . .

The plants have been here for a thousand times longer than modern humans, preparing the way for us by:

creating the air we breath,
    stabilizing the planetary climate,
        feeding us from sunlight,
and, teaching us to:		
    "stand tall" like a redwood,
        "bloom" like a rose, 
            and "bear fruit" in due season.

My earliest memories are of kneeling in the spring soil with my mother and planting sweetpea seeds. Watching them grow into beautiful and fragrant flowers was as "close to magic" as it could get for a four-year old.

I felt that the Walk Through Time wouldn't be complete without giving the green plants a chance to speak for themselves.

Rick Walker


Station I

. .

Life makes its first successful attempts to colonize the dry land around 1.5 billion years ago.

This boulder, a Sonoma fieldstone, is covered with lichen, one of the most fascinating descendents of these first explorers.

Lichens are a cooperative partnership between a fungus and a photosynthetic green algae. The lichen secretes an acid which dissolves the rock, breaking it down into soil which can be used later by other plants:

The sponge-like fungus 
    catches the dew,
Encouraging its companion 
    to exuberant photosynthesis,
Nourishing both participants, 
And in the process, 
    makes a way for future travellers.

Station II

. .

Lichens, bacteria, and weathering transform the once bleak landscape. The stage is set for more complex plants to develop.

Club-Mosses are the next dominant species, becoming common in the fossil record about 450 million years ago. The dead bodies of these mosses enable the soil to retain more water and further improve the ability of the land to support life.

The grey limestone used here was formed from the calcified shells of marine organisms which lived in shallow seas worldwide.

The sheer weight of these deposits, sinking into the earth's crust, help to shape and form the continents.

The central whisk-like plant is Psilotum nudum. Lacking both roots and leaves, it is thought to be a missing-link between mosses and ferns. The darkened nodules on the stems are spore-capsules.

The fine moss used in the foreground is an unidentified local moss common here in the bay area.

The larger unidentified moss was propagated from samples collected at Polhemus Bog, New Jersey.

Station III

. .

Ferns are among the first plants to develop internal plumbing: a network of tubes that carry food and water to all of their cells.

As roads and highways support human culture, the internal plumbing of the ferns enable complex plants to develop.

Internal plumbing continues on into all more complex plants. Later on, Animals innovate even further using an active pump, the heart, to circulate the blood, distributing food and eliminating waste products.

The ground-hugging rosetted fern in the rock is Blechnum spicant, the "Deer tongue fern" common in moist places near redwoods.

The foreground fern is Selaginella pallescens, the "Resurrection Fern". These specimens are propagated from material collected in the Sinaloa State of Mexico by Berkeley Botanical gardens in 1959.

The tall fern is unidentified, and was grown from spores present in a bale of New Zealand sphagnum moss.

Station IV


300 million years ago the towering 50-foot tall Horsetails exploit the vertical dimension. These small plants descend from these original giants.

Most of our fuels, such as the Coal chunk shown here, are actually "fossilized sunshine", photosynthetically stored by plants that grew during this period.

This ancient store of energy has fueled the recent explosion in human technology. We con- sume these fossil resources one million times faster than they were originally deposited.

The "Giant Horsetail", Equisetum telmateia is common local plant growing along streams in moist soil.

Station V

. .

Cycads were so common 200 million years ago that the era is sometimes called "the age of Cycads and Dinosaurs."

Cycads depend on specialized insects to pollinate their intricate cone-like flowers. Widespread use of pesticides has killed many of these insects, putting the cycads themselves at risk of extinction.

The uniform distribution of cycad fossils worldwide supports the Pangea theory that all the continents were once connected together in a single, unbroken landmass.

Extensive collisions between the drifting continental plates along the western margin of North America generated the granite cobbles used in the companion planting.

The largest plant shown here, Cycas revoluta, was collected at Okinawa by Berkeley Botanical Gardens in 1987.

Station VI

. .

The majestic Dawn Redwood reaches a height of 300 feet or more, with a life-span of several thousand years.

Redwoods belong to "climax" ecosystems, existing only because a succession of other organisms prepared the soil for million of years before their arrival.

The Dawn Redwood was first discovered in California fossil beds, and was thought to be extinct for 50 Million years.

In 1948, botanical explorers found three live trees in a lush, fog-shrouded valley deep in China and 7 more specimens a few years later. Horticulturists have since spread this tree throughout the world.

The Dawn Redwood is Metasequoia glyptostroboides.

Station VII

. . .

The complex web of life on Earth, gradually built up over 5 billion years, provides a stable self-governing home for human development.

In the last 200 years, a blink of the eye in geologic time, human activity has increased until it threatens to disrupt the stability of our planet's life system.

Is it now time for Humankind to move out of adolescence, and into mature adulthood? Maturity is signalled in a young adult when attention turns away from self-centeredness towards community service and future planning.

The Ecosphere in this display is a self-sustaining model of the Earth's biosphere. Filled with seawater, Hawaiian cave shrimp, green algae, and marine snails, it requires only a source of light, warmth, and human protection for its continued existence.

Rick Walker
rick_walker "AT"