Two Species of Alethopteris From Iowa Coal Balls
Iowa coal ball shows the venation characteristic of Alethopteris .ml livanti (Fig. I). The density of secondary veins is 2225 veins per 'Department of Botany, University of Iowa, Iowa City, Iowa S2242 femlike compression foliage. Most subsequent studies of the genus have been confined to compression material. A summary of this work is found ...