The third volume of Albert Charles Seward's paleobotanical textbook opens with an extensive examination of recent Cycads, analyzing their morphology, stem anatomy, foliar bundles, and reproductive structures as a baseline for understanding extinct forms. The author details the geographical distribution and longevity of surviving cycadean genera, including Cycas, Zamia, Encephalartos, and Bowenia, while contrasting their anatomical features with those of fossil plants. The discussion then transitions to the foundational groups of Pteridosperms, beginning with the Lyginopterideae. Seward provides a meticulous breakdown of the vegetative and reproductive organs of Lyginopteris, examining the stem structure, the glandular fronds of Sphenopteris, the microsporangia of Crossotheca, and the seminal structures of Lagenostoma.
A parallel investigation is conducted on the genus Heterangium, tracing its anatomical similarities and differences relative to Lyginopteris and highlighting the associated reproductive structures. The study advances to the Medulloseae, exploring the complex polystelic stelar systems found in Medullosa, Colpoxylon, and related genera, alongside their Myeloxylon petioles and Trigonocarpus seeds. Throughout the work, Seward addresses the evolutionary and phylogenetic links between Paleozoic seed ferns and modern gymnosperms, particularly the Cycadales, while reviewing various problematic fructifications and unclassified stems from the Carboniferous and Permian periods.
