Published online by Cambridge University Press: 05 December 2011
An unusual form of Asplenium adiantum-nigrum from Scottish and European serpentine sites has been grown for several years under uniform conditions of culture alongside A. adiantum-nigrum of nonserpentine origin, and has been found to retain its characteristic features. The morphological distinctiveness of both types, apparent in juvenile as well as adult plants, has been maintained through successive generations.
Transplant experiments were carried out in order to determine whether serpentine and non-serpentine plants differed also in their physiological response to soil factors. The results suggest that serpentine soils are unfavourable to the growth of non-serpentine A. adiantum-nigrum, particularly at germination and during the early development of the sporophyte. Soil analysis data are presented and briefly discussed.
The experimental evidence presented here, combined with the constancy of the diagnostic differences leading to ease of recognition of the serpentine forms at all ages, suggests that evolution leading to the establishment of ecologically adapted divergent strains is actively in progress.