Mosses and their relatives

            Mosses, like ferns, are green plants which produce spores. Spores grow into the kind of plants that produce two special kinds of cells. One kind swims over to the other. When these two join a new moss plant can grow. Most mosses live on land. Unlike ferns, they do not have true stems and roots. They have parts that look like stems and roots, but there are no tubes inside. Soil water, and minerals cannot flow up easily. They have to soak their way up from cell to cell.

The lower plants

            There is another group of plants that do not make seeds. These plants are called “lower plants” because they are simple in structure and appeared early in the history of life on earth. Botanists divide these lower plants into two groups: (1) those that have chlorophyll are called algae (2) those that have no chlorophyll are called fungi. Algae are lower plants that are found in puddles, streams, ponds, oceans, and in all the wet places of the world. Many of them are so small that they can be seen only with a microscope.  Some algae have other colored substances besides chlorophyll. These colors hide the green chlorophyll and make the algae look brown, yellow, or red. But because all algae have chlorophyll, they can make their own food out of carbon dioxide and water in sunshine. Not all algae are tiny. Giant kelp may be 100 feet long. Millions and millions of tiny algae float on the sea. In some parts of the ocean there are so many algae that the surface looks like a green meadow. Molds are fungi with many cells. Some of these cells form rootlike structures that work their way into the mold’s food supply. Some cells form stemlike structures. Cells at the top of these “stems” produce spores. Thousands of tiny powdery spores are released into the air. If they land in a suitable spot, each spore can grow into a new mold plant. Yeasts are another group of fungi. They are one-celled. The little bumps that grow on a yeast call are called buds. They break off and become new yeast cells. Yeasts are useful in many ways in preparing foods.

Plant puzzles

            There are many puzzles in the plant world. Many plants are not easily classified into groups. They are classified as “in-betweens.”
            Lichens. These plants are found on rocks and on the bark of trees. They can grow in very cold climates where hardly any other living thing can grow. If we look at a lichen under a microscope, we can see that it is really two plants – an algae and a fungus. The alga with its green chlorophyll makes food. The fungus provides minerals and water which the alga needs to make food.
            Slime molds are very simple living things. They have no cell walls. They flow over food and take the particles into themselves. In this way the slime mold is like a very simple animal, the amoeba. But during part of its life cycle the slime mold divides into thousands of separate cells. Each has a cell wall. Some of the cells make spores that can develop into new slime molds.
            Bacteria. The biggest puzzle in classification is the group of living things called bacteria. There are thousands of different kinds, but all are alike in these ways: (1) they are single cells (2) they are very small – the largest is about 1/500 of an inch long. The smallest is so tiny that you could put 250,000 in a row on this line _________ (3) they grow to full size and then divide into two. The most useful system of classification is by structure. Let’s look at the structure of bacteria: (1) they have cell walls. They do not have a definite nucleus. In these ways they resemble the simplest kind of algae. However: (2) algae contain chlorophyll, while bacteria do not. In this way, bacteria resemble fungi. However: (3) some kinds of bacteria have threadlike muscular fibers that whip from side to side and provide motion through water and other liquids. This way of moving is very common among many one-celled animals. However: (4) bacteria have cell walls around their cell membranes, while animal cells do not. So how do we classify bacteria? Many botanists believe that they should be classified as a third group of lower plants. The three principal groups of bacteria are bacilli, cocci, and spirilla.

Plants with Cones

            Pine, fir, and spruce trees have seeds, but they have no flowers. Their seeds are made in cones. There are two kinds of cones that grow on a pine tree: pollen cones and seed cones. Pollen cones have pollen but no ovules. Seed cones have ovules but no pollen. The ovules can grow into seeds only when pollen reaches them. Wind blows the pollen around. Some of it falls on the seed cones and gets between the scales. It reaches the ovules that grow into seeds inside the cone. When the seeds are ripe, the pine cone opens. The cone is the fruit of the pine tree. It holds the plant’s seeds.