1989, Douglas E. Soltis, Pamela S. Soltis, Chapter 12: Polyploidy, Breeding Systems, and Genetic Differentiation in Homosporous Pteridophytes, Douglas E. Soltis, Pamela S. Soltis (editors), Isozymes in Plant Biology, page 241,Most pteridophytes are homosporous, producing one type of spore that germinates to produce a potentially bisexual gametophyte.
1990, A. C. Jermy, Conservation of Ppteridophytes, K.U. Kramer, Klaus Kubitzki, P.S. Green, Pteridophytes and Gymnosperms, page 14,Pteridophytes have evolved to fill almost every ecological niche but the greatest species diversity is clearly found in the tropical rainforest. The rapid disappearance of this biome throughout the world with many of their pteridophyte species yet undiscovered, let alone described, is of great concern.
2004, Pooja, Pteridophyta, page 13,Pteridophytes are known from as far back as the Silurian, or some 380 million years ago. During the Silurian and the immediately succeeding Lower Devonian there were a considerable number of psilophytes of much simpler construction than any other known type of pteridophyte.
