Physiology of the Reproduction of Bryophytes

That the periodicity of vegetative and sexual reproduction in bryophytes is conditioned by external factors has now been demonstrated by many authors. Some of the earlier work has been reviewed in a previous paper by Benson-Evans (1961). Other contributions have been made by Gorton and Eakin (1957); Mitra, Allsopp, and Wareing (1959); Bopp (1963); Kofler, Dutel, and Nurit (1963); and Vaarama and Tarkn (1963), all of whom have investigated factors controlling germinating spores, protonemal growth, and bud formation in mosses. Rhythms in later stages of vegetative growth leading up to production of sexual branches have been described by Tallis (1958, 1959), and the effects of day length on the development of the sporophyte have been shown by Hughes (1962). Mohr (1963), Steiner (1963), and Schwabe and Nachmony-Bascomb (1963) have added useful information on factors controlling early development of young thalli and gemmae in liverworts, and Anthony (1962) on the production of gametangia. It is the purpose of the present article to demonstrate the main environmental factors conditioning sexual reproduction in the bryophytes, with particular reference to the liverworts, by presenting data derived from field observations and laboratory experiments carried out at Cardiff.