Nothia aphylla: The Issue of Clonal Development in Early Land Plants

The Early Devonian herbaceous plant Nothia aphylla from the Rhynie Chert (Aberdeenshire, Scotland) is a striking and informative example of a developmental strategy in early land plants. Although simple and primitive in anatomy, N. aphylla combined sexual and vegetative reproduction in order to survive and colonize moist patches near ponds and hot springs in an alluvial plain. Large colonies formed, being mainly composed of clonal individuals derived from asexual reproduction, i.e., the separation of similar units created by lateral branching. Each unit consisted of a single rhizome bearing one ventral, rhizoidal ridge and one distal, aerial, photosynthetic, and fertile branched shoot. The rhizomes allowed for an indeterminate horizontal propagation, while the erect photosynthetic shoots furnished a limited vertical occupation. Similar architecture and clonal development existed among coeval plants, such as Aglaophyton major and Horneophyton lignieri, and persisted through geologic time. Nowadays asexual reproduction is still a successful strategy in bryophytes, pteridophytes, and angiosperms.