Article: Amyelon in American coal-balls
Premnoxylon iowense Pierce and Hall is recombined as Amyelon iowense. These cordaitean roots resemble the stilt roots of modern mangroves. They are usually siphonostelic and possess aerenchyma composed of phloem and phelloderm. Increase in circumference of a deep-seated periderm distended the outer part of the phloem. Aerenchymatous phelloderm was laid down and cortex was sloughed; leaving periderm the outermost tissue. Lenticels flank clusters of lateral rootlets.