Liverwort

The liverwort is a non-vascular plant with between 6000 and 8000 different species. Its name comes from the liver shaped lobes. In the 16th century it was a popular belief that God had appointed a sign for each plant to identify its medicinal value. It was therefore believed to have healing values for the liver. Evolutionists believe that the liverwort arose as green algae 400 million years. They call it one of the simplest true plants. 

Anatomy
The liverwort is a small green plant which grows close to the ground. It has two different life cycles: the dominant gametophyte stage and then the sporophyte stage. 

The gametophytes' size is between 0.15 mm and 2.5 cm in width and 2 mm to 25 cm in length. The gametophyte appears in either the leafy form or the thallose form. The thallose liverwort is flat with slightly wavy margins. The leafy form has small hair-like leaves coming from a tiny stem.

The sporophyte grows on top of, or out of, the gametophyte. It is composed of the seta, the long stem or stalk coming out of the base, and a sporangium, the capsule on the top. A mature seta will reach two to three inches up into the air. 

Instead of having roots liverworts have rhizoids, which are only one cell thick appendages which anchor them into the ground. 

Reproduction
Liverworts can produce both sexually and asexually.

Sexual Reproduction


A liverwort reproduces through the alternation of generations, wherein the plant alternates between a gametophyte (which produces gametes) and a sporophyte (which produces spores). The gametophyte develops either antheridia, the male organs, or archegonia, the female organs. They are very small and develop either in the umbrella like structure or on the underside of the leaves. Both the thallose and the leafy liverwort require water for reproduction, but use it in different ways. The thallose group depends on rain drops to send their sperm flying in the air to meet a female plant's archegonia. The leafy liverwort sperm moves across a thin layer of water to get to the archegonia. After the sperm has reached the female's archegonia fertilization takes place. Soon a sporophyte begins to grow out of the gametophyte. The seta, the stalk of a sporophyte begins to lift the sporangium containing spores up into the air. The spores are released when the sporangium splits open and then they have the opportunity to create a new gametophyte.

Asexual Reproduction


The gametophyte can also reproduce two different ways asexually. Vegetative reproduction begins when a leaf or other part of the plant gets separated from the rest of the plant. It can then grow up into a new plant. The other way a liverwort can reproduce is through gametes. In thallose liverworts gamma cups grow on the leaves and fill with gametes, haploid sex cells. The gametes are released into the surrounding area when water droplets hit the gamma cup. If condition are favorable they can grow into a new plant. 

Ecology
Liverworts are found mostly in the Northern Hemisphere in forest regions. Since they require water for reproduction their habitat must be moist and have a source of rain or water, for this reason they thrive in the Pacific Northwest especially. They are found in clumps around each other in moist, shaded areas, often under plants. Some liverworts are aquatic and can be found in living on the water's surface. 

Liverworts contribute to their biome in the fact that they are apart of the nutrient cycle and they provide a home to many small insects and microorganisms.

Subclass Jungermanniae
 Order Calobryales
 * Families
 * Haplomitriaceae
 * Acrobolbaceae
 * Antheliaceae
 * Arnelliaceae
 * Calypogeiaceae
 * Cephaloziaceae
 * Cephaloziellaceae
 * Chonecoleaceae
 * Geocalycaceae
 * Gymnomitriaceae
 * Gyrothyraceae
 * Herbertaceae
 * Jubulaceae
 * Jungermanniaceae
 * Lejeuneacea
 * Lepidoziaceae
 * Mastigophoraceae
 * Mesoptychiaceae
 * Plagiochilaceae
 * Pleuroziaceae
 * Porellaceae
 * Pseudolepicoleacea
 * Ptilidiaceae
 * Radulaceae
 * Scapaniaceae
 * Trichocoleaceae

Order Jungermanniales
 * Families
 * Acrobolbaceae
 * Antheliaceae
 * Arnelliaceae
 * Calypogeiaceae
 * Cephaloziaceae
 * Cephaloziellaceae
 * Chonecoleaceae
 * Geocalycaceae
 * Gymnomitriaceae
 * Gyrothyraceae
 * Herbertaceae
 * Jubulaceae
 * Jungermanniaceae
 * Lejeuneaceae
 * Lepidoziaceae
 * Mastigophoraceae
 * Mesoptychiaceae
 * Plagiochilaceae
 * Pleuroziaceae
 * Porellaceae
 * Pseudolepicoleaceae
 * Ptilidiaceae
 * Radulaceae
 * Scapaniaceae
 * Trichocoleaceae

Order Metzgeriales
 * Families
 * Allisoniaceae
 * Aneuraceae
 * Blasiaceae
 * Fossombroniaceae
 * Metzgeriaceae
 * Pallaviciniaceae
 * Pelliaceae
 * Treubiaceae

Subclass Marchantiae
Order Marchantiales (Thallose liverworts)
 * Families
 * Aytoniaceae
 * Cleveaceae
 * Conocephalaceae
 * Corsiniaceae
 * Lunulariaceae
 * Marchantiaceae
 * Monosoleniaceae
 * Oxymitraceae
 * Ricciaceae
 * Targioniaceae

Order Sphaerocarpales
 * Families
 * Riellaceae
 * Sphaerocarpaceae