Most people are unaware of hornworts, though they are a quite common and widespread group of plants which may be found in tropical forests, along streamsides, and in disturbed fields around the world. Most species are small and unassuming greasy blue-green patches, but some tropical species can cover large areas of soil or the sides of trees. Because of their unique morphology, there have been many questions about relationships and origin of the Anthocerotophyta.
Hornworts are a very unusual group of plants.
This continuous growth from a near-basal meristem is unique among plants to hornworts. As the sporophyte grows longer, it splits into two halves lengthwise, releasing the spores as they mature. Along with the spores are cells called pseudoelaters , which change shape as they dry out and thereby assist in scattering the spores. When a spore germinates, it produces a flat thalloid plant with a greasy blue-green color and odd morphology. This is an especially useful character for sterile material, but you must look at fresh material, since hornworts tend to dry up and fall apart if not kept moist, and will quickly rot if immersed.