The gametophores of Sphagnum spp. normally grow on peat and in oligotrophic waters, but attempts to grow the protonemata of S. papillosum, S. cuspidatum and S. magellanicum in natural waters failed. When the spores were sown on a cellophane disc in contact with a standard culture solution in special culture chambers however, protonemata consisting of a thallus with filaments developed from the spores of all three species. When the culture solution was diluted × 10, × 100 and × 1000, the size of the thalloid part of the protonemata became progressively less and the filamentous part was relatively more extensive. S. magellanicum failed to germinate when the solution was diluted × 100. The effect of reducing the concentration of each of the major ions individually was investigated and it was found that the thallus decreased in size as the concentration of phosphate was decreased. The protonemata failed to respond in a consistent way to nitrate and developed satisfactorily in the complete absence of the ion.
Natural waters were collected from five ombrotrophic mire sites in Scotland and the phosphate level raised to that of the 0.1 standard solution by adding sodium dihydrogen phosphate. In about half of the cultures (spread throughout the five waters) the form of the protonemata (S. papillosum only) was similar to that of protonemata in 0.1 standard cultures. When spores were immersed in culture solution, very small protonemata only developed.
It is concluded that protonemata of the species of Sphagnum used are unlikely to develop in mire pools because (a) the concentration of phosphate is too low and (b) the protonemata are unable to develop properly when completely immersed.