1. Allen, R. F. Studies in spermatogenesis and apogamy in ferns. Transactions Wisconsin Acad. Sc. 17, 1911, 1–56.
2. Andersson-Kottö, Irma, The genetics of ferns. Bibliographia genetica 8, 1931, 269–294.
3. Andersson-Kottö, I. and Gairdner A. E., The inheritance of apospory on Scolopendrium vulgare. Journal of Genetics 32, 1936, 189–228.
4. Baranov, P., Entwicklungsgeschichte des Sporangiums und der Sporen von Lycopodium clavatum L. Ber. D. Bot. Ges. 43, 1925, 352–360.
5. Bartoo, D. R., Development of sporangium in Schizaea rupestris. Bot. Gaz. 88, 1929, 322–331.