Evolutionary history of plants and radially symmetrical, is an integumented megasporangium surrounded by a cupule. The megasporangium bears an unopened distal extension protruding above the multilobed integument. It is suspected that the extension was involved in anemophilous pollination. "Runcaria" sheds new light on the sequence of character acquisition leading to the seed. "Runcaria" has all of the qualities of seed plants except for a solid seed coat and a system to guide the pollen to the ovule. The first spermatophytes (literally: "seed plants") – that is, the first plants to bear true seeds – are called pteridosperms: literally, "seed ferns", so called because their
Evolutionary history of plants such as "Rhynia" preserved in the Rhynie chert is of similar complexity, which is taken to support this hypothesis. By contrast, with the exception of "Psilotum" modern vascular plants have heteromorphic sporophytes and gametophytes in which the gametophytes rarely have any vascular tissue. There is no evidence that early land plants of the Silurian and early Devonian had roots, although fossil evidence of rhizoids occurs for several species, such as "Horneophyton". The earliest land plants did not have vascular systems for transport of water and nutrients either. "Aglaophyton", a rootless vascular plant known from Devonian fossils in the Rhynie chert