Vein reticulation in seed ferns of the Dobrudzha coalfield Bulgaria

Abstract

Alethopteris, Lonchopteris, Paripteris, Linopteris and Reticulopteris are abundant pteridosperm fronds in the Pennsylvanian-age Dobrudzha Coalfield. The transition from fan-shape to reticulate veining in Lonchopteris, Linopteris and Reticulopteris and in Laveineopteris to Reticulopteris is documented. The most probable cause for this is the decrease in humidity; in addition to temperature controls on the geographic distribution. The form and positioning of anastomoses are discussed.