Methodology:

In July 2010, August 2011, July 2012 and August 2015, 140 specimens of 13 leafy liverwort species were collected from eight sites on Broggerhalvoya and Blomstrandhalvoya on Spitsbergen in the High Arctic archipelago of Svalbard.The plants were dried at room temperature and were subsequently rehydrated in water and cleared in 10% KOH for 24 h. They were then rinsed thoroughly with water and were bleached in a mixture of 30% hydrogen peroxide and 3% ammonium hydroxide (10:1 v/v) for up to 10 min. The plants were then washed thoroughly with water, were acidified in 5% lactic acid for 1 h and were stained with 0.01% aniline blue in lactic acid for 24 h. They were then removed from the staining solution, excess stain was drawn off on absorbent paper, and the plants were destained for at least 24 h in 80% lactic acid. Between 10 and 15 stems of each species, and at least 40 stems of C. varians and C. bicuspidata, were then lightly squashed in 80% lactic acid on glass slides prior to observation under UV epifluorescence at x 400 magnification (BX51 microscope, Olympus UK Ltd). Using the line intersection method described by McGonigle et al. (1990, New Phytologist 155, 495-501), the percentages of stem length colonised by hyphal coils (in rhizoid bases and stem epidermal cells), hyaline septate hyphae (in stem epidermal cells) and dark septate hyphae (on stem surfaces) were calculated. At least 50 intersections were scored in each specimen. The percentage of c. 30 rhizoids in each specimen that were colonised by hyaline hyphae was also recorded.

Data collection:

BX51 microscope, Olympus UK Ltd

Data quality:

Raw data are shown. The data have not been cleaned. Missing data in the 'Rhizoids_colonised_percentage' column (indicating that no rhizoids were observed on the stems of plants) are indicated by NA.