The Nematophytes are a group of land organisms, probably plants (although their biochemistry is consistent with an algal affnity), known only from the fossil record, from the Silurian period until the early Devonian Rhynie chert. Its type genus Nematothallus, which typifies the group, was first described by Lang in 1933, who envisioned it being a thallose plant with tubular features and sporophytes, covered by a cuticle which preserved impressions of the underlying cells. He had found abundant disaggregated remains of all three features, none of which were connected to another, leaving his reconstruction of the phytodebris as parts of a single organism highly conjectural.
The lack of a clear definition of the nematophytes has led to it being used as a wastebasket form taxon, with all manner of tubes and cell-patterned cuticles from around the Silurian being dubbed "Nematophytic" more as a statement of ignorance than as a scientifically meaningful statement.
Linnean taxonomy struggles to accommodate most fossil groups, as they tend to form stem groups to modern taxa. Thus despite Strother's attempts to formalise the nomenclature of Nematothalli, the hierarchy of class, order and family are better thought of as a stem group to the embryophytes (modern land plants), with the green algæ a stem group to the Nematophytes in turn. Indeed, since no reproductive or vegetative structures common to the land plants are seen, it may not be safe even to assume this relationship.