The Lower Plants The Lower Plants may be better referred to as the ancient plants because they were the first plants to come out of the sea billions of years ago. Having preceded the seed-bearing, higher plants, they are all non-flowering. Most of the lower plants reproduce both asexually and sexually via spores, in a process known as alternation of generations (see separate sheet). ALGAE AND LIVERWORTS One of the first green plants forming in the sea was probably algae. Seaweeds are algae, as is the scum on ponds and green slime on rocks. The green color we see in the Rivanna Reservoir in the summer is caused by algae growth. Algae is usually a water plant and reproduce mainly by simple cell division. The first green land plant is usually awarded to the liverworts. Each liverwort plant is only an inch or two long and no thicker than a piece of paper. It is made up of several layers of cells, each with its own job to do. The top layer is the skin, preventing evaporation of water. Food is manufactured in the middle layer while the bottom layer anchors the liverwort in place with hair-thin threads. Liverworts creep over rocks, growing from the tips while dying at the base, so that they never grow very long. They need damp, shady places and are often found along streams and in the woods. Like algae, reproduction is mainly by cell division. LICHENS Lichens don't really fit into the evolutionary picture very well. They have no leaves, stems or roots. They are in fact 2 plants in one. Lichens consist of a green, photosynthesizing alga living symbiotically with colorless fungus. 'Me alga makes the food for both while the fungus wraps itself around the alga protecting and anchoring it. Lichens live on rocks, on bark, on tops of mountains, and even on the tundra. Neither could live without the other in such places. Common lichens found at Ivy Creek include Parmelias, found on the trunks of trees and rocks, and the stalked lichens of the genus Cladonia such as Reindeer moss (not a moss), Pixie Cups and British Soldiers (the red knobs are where the spores are formed). In ancient time, lichens were cooked to make blue and red dyes. This led to the discovery of its power as litmus paper, an indicator for acids and bases still used in laboratories today. Likewise, its dyes are used in Harris tweed. Lichens are considered “pioneer plants” initiating processes of soil formation in places no other plants can grow. The tiny threads associated with the fungus dig deep into the rock, releasing a weak acid, slowly dissolving the rock. In wet weather, these cracks swell with moisture, further breaking the rock down. As the lichens die, the dead plant and rock material combine to form soil. After a time, there is enough soil to support moss, then ferns, then flowers and grasses. Ultimately trees will move in. This is called succession. This process goes on around you everyday, everywhere. While the fungus forms spores, this is not a reliable way for lichens to reproduce. They depend much more on new plants sprouting from old and wind-borne “buds,” in which each bud contains both the alga and the fungus. Despite their hardiness in harsh climates, lichens are extremely sensitive to man-made pollution, particularly sulfur dioxide. Their growth and development is used as in indicator of air pollution. FUNGUS Fungi, are in some ways, even more polypores have invaded the tree probably via a primitive than liverworts, because within a fungus, wound. When established, the mycelium will feed every cell is like every other. It has no outer on the tree, digesting the wood until it becomes protective skin and no roots, leaves or soft and crumbly. It is difficult to root out a chlorophyll - therefore no way to make or store growing shelf fungus. food. Yet fungi have been around for at least two billion years and there are five times as many Many mushrooms have gills under the cap different fungi as there are mosses, lichen and and above the stem of the fruiting body. The gills, ferns. Mushrooms, mildew, yeasts, plant rusts, and containing the spores, are hidden until the mold, such as penicillin are all fungi. umbrella is wide open at which time the spores The mushroom you eat is the short-lived rain out - billions of them - either dropping to the fruiting body of a fungus, the container of spores. ground below or blowing away with the wind. As The main part of the fungus plant lives on the spores ripen, the gills melt away, dissolving underground as fine root-like threads, known as into an ink-like liquid, which actually helps to carry hyphae, branching and spreading, sometimes for away the spores. miles, into a network known as the mycelium. Via Not all fungi are umbrella-shaped. Shelf or the hyphae, fungi feed on living and dead matter Bracket Fungi stick straight out of the wood on around them - decaying leaves, rotted wood, which they grow. These mushrooms do not have sometimes living tissue. gills - they have thousands of tiny holes (pores). In this way, mushrooms play a very Each pore is the mouth of a hollow tube. The important role in the process of decomposition. spores develop inside these tubes, dropping out They are the first of the decayers to invade dead when ripe. The Polypore mushrooms refer to this wood and leaves. Look at a fallen log and notice the structure. mushrooms that grow on it. Through their Some mushrooms develop spores on small, expanding mycelium, fungi release enzymes that fleshy teeth, others on upright branches. Spores of break down the complex carbohydrates found in the cone-shaped Morel mushroom develop in their nature into simpler components and carbon characteristic wrinkles and ridges. dioxide, making them once again available to Others form spores inside their caps. plants for growth. After the fungi soften the wood, Puffballs form a round ball on the surface of the secondary decayers can move in to accelerate the ground, which disintegrates when the spores are return of the log to soil. ripened. By tapping a ripened puffball, one can see Unfortunately, this enzyme action works on the “smoke” of spores erupt out. live wood, too. Mushrooms commonly seen on an Ivy Creek tour are the shelf fungi. When seen on a live tree it is bad news. The spores of these Reference: The Story of Mosses, Ferns and Mushrooms by D. Sterling, 1955 The World Book Encyclopedia, 1990 How Nature Works by S. Parker, 1993 MOSSES Mosses take another leap up the Mosses are important pioneer plants on evolutionary ladder. like algae and liverworts, near-bare landscapes, as they will grow in very mosses reproduce asexually, both from the tips shallow soil, preventing erosion and building up of last year’s plant and via underground the soil as they die. rhizomes. However, they also reproduce sexually via spores. See Spore Reproduction and Moss Life Cycle. Mosses have no roots (they have hair-thin threads known as rhizoid) and no vascular system, and thus have no way to store food or water. Furthermore, their chlorophyll will dry up in bright sunlight. Therefore mosses have adapted unique survival techniques. When stressed, mosses curl up, protecting their chlorophyll, and basically shut down making The most common mosses at Ivy Creek them look dull and gray. When water becomes Natural Area are Hairy Cap, Fern moss and Pin- available again, the moss will unfold to reveal its Cushion Moss. true green self again. FERNS ALLIES Horsetails and Club mosses were the first green plants to shoot up into the air - 60, 80, 100 feet tall back in the Coal Age. Today, these fern allies are miniatures of their ancient selves, measuring 6 inches to 6 feet. Horsetails grow in poor soil from an underground stem, producing two different- looking stalks each season. The first are on jointed, hollow stems looking like pieces of pipe fit together. Nourishment comes from stored food in the underground stem. Their only purpose is to produce spores. The second stalk to come up is the food- making stalk. They are bushy plants with a circle of Running cedar is the most common club moss green branches looking like a horses’ tail. found at Ivy Creek. Because people over harvested it as Christmas decoration for years, it became a Club mosses need the rich soil of the woods. protected plant and is now coming back. The Once the size of trees, these plants now are spores, having a very high wax content, were used creeping plants with trailing or underground in old-time photography to make a flash. The stems. Spores are formed at the base of the leaves, spores also made fine talc for surgical gloves. The on separate stalks or in erect cones. See alternation plant itself has a high enough wax content to make of generations. it a fire risk when dried as a wreath. FERNS From an evolution point of view, ferns are at REPRODUCTION the top of the lower plants ladder. Their leaves are Ferns, like most flowerless plants, bigger, their stems sturdier and their roots tougher reproduce via spores, having both a sexual and than the other lower plants. They are just one step asexual phase. This is called alternation of below the flowering plants (seed-bearers). generations. See Fern Life Cycle. In the sexual phase, when a fern spore LEAVES germinates, it grows into a prothallus, a green The appearance of the leaves, known as heart-shaped plant about the size of a thumbnail, fronds, is one of the identification markers for the looking much like a liverwort - and nothing like its different ferns.