Lycopodiopsida

Some plants look like moss.

They have small leaves. These leaves grow on stems.

They make tiny seeds called spores. The spores grow on the sides of the stems. Long ago, these plants grew into huge trees. These giant trees made the coal we use today.

Some spores can even help make fireworks. These plants are very old and special.

Lycophytes are a special group of plants.

Some people call them clubmosses or spikemosses. They have tiny leaves called microphylls. These leaves grow on stems that branch out.

Instead of seeds, these plants make spores. These spores grow in small parts called sporangia. The sporangia sit on the sides of the stems.

These plants have a very long history. They first appeared a long time ago in the Silurian period. Some grew into giant trees.

One type of tree was called Lepidodendron. These trees formed huge forests. They lived in wet areas. When these trees died, they helped make coal.

You can even see their shapes in rock fossils today.

Some lycophytes live with tiny fungi in the soil. These fungi help the plants grow. Some fungi living inside the plants make medicine. This medicine can help people with brain health. Lycophyte spores can also catch fire easily. People have used them to make fireworks.

Lycophytes are a special group of vascular plants.

You might know them as clubmosses, spikemosses, or quillworts. These plants have a unique way of growing. Their stems branch out in a pattern called dichotomous branching. They also have tiny leaves called microphylls. These leaves are much simpler than the leaves on most other plants. Instead of seeds, they use spores to make new plants. These spores grow in small containers called sporangia. These containers sit on the sides of the stems near the leaves.

How these plants grow involves many steps. First, the spores are released from the sporangia. Some plants, like spikemosses, have different sizes of spores. They have large female spores and small male spores. These spores grow into a stage called a gametophyte. Many clubmoss gametophytes live underground for several years. They often live with fungi to get food. This way of getting food is called being mycoheterotrophic. Once the plant is ready, it grows into a new sporophyte. Some species even grow the new plant right on the mother plant. They only drop the new plant when it is strong enough to live alone.

These plants have a very long history on Earth. Fossils of lycophytes first appeared during the Silurian period. One of the earliest known species is called Baragwanathia longifolia.

During the Devonian period, some species grew very large. They even grew into trees. In the Carboniferous period, tree-like plants called Lepidodendrales ruled the world. These plants formed huge forests in tropical wetlands. They were different from modern trees because leaves grew all over the trunk. When the leaves fell off, they left diamond-shaped scars behind.

Scientists use different names to group these plants. In 2016, a group called PPG I created a common system. They put all living lycophytes into one class called Lycopodiopsida. This class includes three main orders. The first is Lycopodiales, which contains the clubmosses. The second is Isoetales, which includes the quillworts. The third is Selaginellales, which includes the spikemosses. Other scientists have used different names like Lycophyta or Lycopodiophyta. The way we name them can change depending on which system a scientist uses.

Lycophytes are linked to many things we see today. The remains of ancient tree-like lycophytes created many coal deposits. You can even see fossils in places like Glasgow, Scotland. Some lycophytes help humans through medicine. A fungus living inside a plant called Huperzia serrata makes a compound called Huperzine A. This can be used to treat Alzheimer's Disease. Even the spores have uses. They catch fire very easily. Because of this, people have used them for fireworks and theater effects.

Lycopsids, also known as lycophytes, are a unique class of vascular plants.

This group includes plants commonly called clubmosses, spikemosses, and quillworts. They belong to the class Lycopodiopsida. These plants are distinguished from other vascular plants by their microphylls. Microphylls are very simple leaves. Lycophytes also have sporangia, which are containers that hold spores. Unlike many other plants, these sporangia are located on the sides of the stems. They also open transversely, which means they split sideways rather than lengthwise. These features make them very different from the euphyllophytes, which have larger, more complex leaves.

The life cycle of a lycopsid involves several distinct stages. It begins when spores are released from the sporangia. In the order Lycopodiales, the plants are homosporous, meaning they produce only one type of spore. However, in the orders Isoetales and Selaginellales, the plants are heterosporous. This means they produce two different types of spores: large female spores and small male spores. After fertilization, the female gametophyte produces sporophytes, which are the main plant bodies. Some species, like Selaginella apoda, are even viviparous. In these plants, the gametophyte develops directly on the mother plant. The new sporophyte is only dropped to the ground once its primary shoot and root are developed enough to live independently.

Many lycopsids rely on complex relationships with microbes to survive. Many species form arbuscular mycorrhizal associations. These are connections with fungi that help the plant. Some gametophytes are mycoheterotrophic, meaning they get all their carbon from underground glomalean fungi. This relationship can last for several years while the gametophyte lives underground. Lycophytes also host fungal endophytes, which are fungi that live inside the plant tissues. Some of these endophytes are very important for medicine. For example, an endophytic fungus in the plant Huperzia serrata produces Huperzine A. This compound is used as a drug in China and a dietary supplement in the U.S. to treat Alzheimer's Disease.

The classification of these plants has changed as scientists learn more. In 2016, the Pteridophyte Phylogeny Group (PPG I) created a consensus system. They placed all living lycophytes into the single class Lycopodiopsida. This class is divided into three orders: Lycopodiales, Isoetales, and Selaginellales. Before this, some scientists used different ranks, such as division or subdivision. Other systems might have treated the three orders as three separate classes. Because of these different scientific views, names like Lycophyta or Lycopodiophyta are also used. The exact way we group them often depends on which classification system a researcher follows.

Lycopsids have an incredibly long evolutionary history. Fossils of these plants first appear in the Silurian period. One of the earliest known species is Baragwanathia longifolia.

During the Devonian period, some species began to grow much larger. This group evolved roots independently from the rest of the vascular plants. During the Carboniferous period, lycopsids were the dominant life forms on land. The order Lepidodendrales included tree-like forms like Lepidodendron and Sigillaria. These plants formed massive forests in tropical wetlands. They were much larger than the small clubmosses we see today.

These ancient tree-like lycophytes had very specific growth patterns. Unlike modern trees, their leaves grew out of the entire surface of the trunk and branches. As the plant grew, the leaves fell off. This left behind distinctive diamond-shaped scars on the bark.

The remains of these massive forests eventually formed huge coal deposits.

You can still find fossilized lycophytes in sandstone in places like Glasgow, Scotland. These fossils help scientists understand how the Earth's climate changed. Some researchers believe that Devonian lycopsids drew down enough carbon dioxide to significantly alter the global climate.

Environmental changes have shaped the survival of the lycopsids. During the Pennsylvanian period, these plants reached their maximum diversity. However, the complex ecology of the tropical rainforests collapsed during the Middle Pennsylvanian due to climate changes. In parts of Euramerica, tree-like species went extinct as the climate became much drier. This allowed conifers, ferns, and horsetails to take over. While many died out, some species survived in places like South China. After the massive Permian–Triassic extinction event, some lycopsids like Pleuromeia acted as pioneers to repopulate new habitats. Today, they remain a fascinating link to the deep history of life on Earth.