A portable system for CO2 gas exchange measurements is described which allows determination of photosynthesis and respiration rates of lichens (and mosses) in the field under light, humidity and temperature conditions which are close to ambient. Time periods for enclosure of the thalli in a cuvette of this CO2-porometer for gas exchange measurement are shortened to between 1 and 2 min, so that an experimental influence on their water relations is small. Between the periods of gas exchange measurement, the lichens experience their natural microclimate conditions. Thus, measurements approximate closely the true gas exchange rates of the lichens under natural conditions. Diurnal courses of CO2 exchange of lichens found growing in a Mediterranean habitat in the spring are demonstrated, as determined by this method.

The contact sites of pycnidia and the terminal cells of trichogynes in Cladonia furcata were investigated using either freshly fixed material, or ascomatal primordia and pycnidia from which the gelatinous material either on the primordial surface, or in the pycnidial cavity, had been removed. The sickle-shaped conidia fused, tip first, with the cell wall of trichogynes. Circular holes of about the diameter of the conidia found in the cell walls of trichogynes arise from enzymatic degradation of the wall material by fusing conidia. As the conidia appear to stick on any gelatinous surface material of the thallus the adhesion process is presumed to be unspecific.

The lichen flora of hazel woodland on the island of Eigg off the west coast of Scotland is described. One area is interpreted as representing ancient ‘climax’ woodland partly on account of its rich epiphytic lichen flora. At other sites various levels of exploitation have modified the lichen communities. Site comparison has enabled a number of species to be recognised which may be useful in the recognition of relict hazel woodland in other oceanic areas. The ecology of the indicator species is discussed. Pertusaria alpina Hepp ex Ahles is reported as new to the British Isles.

The lichen flora of natural outcrops, disused quarries and churchyards in the Magnesian Limestone belt of England, which stretches from Nottingham to Tyneside, is described with reference to 50 sites; 106 taxa were encountered. The lichen flora is compared with that of the Carboniferous Limestone in Derbyshire and found to be distinctive, relating particularly to the abundance of less exacting calcicoles. Lecanora campestris subsp. dolomitica, a lichen widespread at the southern end of the outcrop, is described.

Lecanora symmicta var. sorediosa Westman, a soraliate, yellow, crutose lichen frequently found on wood substrata along the sea shores in the arctic and boreal regions of the northern hemisphere, is now generally accepted as a distinct species, and has recently been provided with a new name: Lecanora arae-frigidae R. Sant. Besides usnic acid it contains zeorin, thiophanic acid and two accessory xanthones. The Finnish material of L. symmicta (Ach.) Ach. examined for comparison differs having thiophanic acid inconstant as well as three unknown substances, while lacking one of the xanthones. One specimen of L. orae-frigidae from the White Sea coast in Karelian A. S. S. R. was growing with a small thallus of Lecanora grantii Magnusson, a new record of the latter species for Europe.

Three name changes are proposed for the lichen checklist. Caloplaca heppiana should be called C. flavescens (Huds.)Laundon comb. nov. It is suggested that Coelocaulon muricatum (Ach.)Laundon comb. nov. is a more appropriate name for C. aculeatum subsp. hispidum. The name Schismatomma virgineum should be replaced with S. cretaceum (Hue)Laundon comb. nov.