Tuesday, 10 July 2012

Trip report Rudloe to Collett's Bottom, 30th June 2012

A party of nine explored walls, hedgerows, woods and fields on a blustery but mainly dry day. Rob Randall demonstrated the difficulty of identifying wild roses due to the presence of numerous hybrids. The Common Dog Rose (Rosa canina), the glaucous-leaved dog rose (R. x dumalis) were identified, as well as the unmistakable Field Rose (R.arvensis), with its stigmas extended on a long pin-like style. The pink hybrid of the Red and White Campion was seen growing near both parents: some were infected by the anther smut (Ustilago violacea). Alan Rayner explained that the fungus attacks female flowers and makes them change sex. The resulting anthers are filled with fungal spores instead of pollen. Rob pointed out several plant-galls caused by mites. Chemicals, introduced as the mites suck the plant's sap, cause the plant cells to form unnatural growths that have a typical form for each mite-plant combination, often a small pimple or nail-like growth from the top surface of the leaf. Underneath is a cavity in which the mite lives and feeds. The subtle differences between the different Umbellifers, and between Black Medick and Hop Trefoil were examined as each species was encountered. On the edge of Collett's Bottom Wood, Spiked Star-of-Bethlehem (or 'Bath Asparagus') was in flower. Alan pointed out the mosses Homalothecium sericeum and Anomodon viticulosus growing on dry-stone walls, and Thamnobryum alopecurum and Fissidens taxifolius, typical of our woods. In the wood were fine specimens of Hard Shield Fern and other ferns. A short detour to an adjacent pasture produced a fine Bee Orchid in full flower, growing in a species-rich sward. Pastures like these used to be a common site around Bath, but over the last 30 years many have been abandoned, improved, or planted with trees. On the track towards Slaughterford, Alan spotted an ancient Wayfaring Tree covered in cankers and in lichens tolerant of nitrates, such as Xanthoria parietina and Physcia adscendens.

Thank you Rob

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