Knowles — The Maritime and Marine Lichens of Hoioth. 109 



analogous to those of their natural habitat. The invaders from the orange 

 belt are, as a rule, only associated witli V. maura aloug the upper limits.; but 

 on the flat shores of Broad Strand, and in several other sheltered localities, 

 Placodinm murovum and Lecanora prosechoides were seen in places spotting the 

 dark crusts of V. maura throughout its whole range. Vernicaria maura normally 

 forms extensive stretches of pure growth about the middle of its range, and 

 seems to be best developed in rather exposed and sunny situations. It grows 

 on both flat and sloping rocks, on smooth and broken surfaces, on the quartzites 

 and on the shales, covering them with a close, dark, scaly crust. It avoids the 

 pure quartz bands, and when growing on the coarse-grained quartzites and 

 grits the thallus is always thin and scattered, being often indicated only by a 

 faint brownish stain. The whole V. maura belt is submei'ged only during the 

 highest spring-tides; but even during these periods tlie upper part of the belt 

 is covered only for a very short time each day, and in calm weather in summer, 

 during neap-tides, the main part of the belt is often left exposed for a long 

 time. Where V. maura grows under drier conditions than usual, the thallus 

 is much more finely areolated and scabrid. Weddell has named this form 

 var. aractina. On the dry sunny shores of Broad Strand var. aractina forms 

 a narrow zone along the upper part of the belt, but it was not noticed on the 

 cliffs. Towards the lower limits of its range, where it is more often wetted by 

 the sea, and in sliade, V. maura gradually passes into the var. memnonia, 

 which is characterized by having the thallus more gelatinous, and almost 

 devoid of areolations. 



The natural habitat of V. memnonia is the lower part of tho V. maura belt ; 

 but on shady cliffs it seems sometimes almost to replace V. maura. It is 

 most commonly seen on the cliffs, where it may be distinctly traced as a 

 narrow zone immediately below V. maura, from which it is easily distinguished 

 by its more shiny thallus. On the shady side of Drumleck Point, at Worn 

 Hole, and at various otlier parts of the coast, V. memnonia forms good colonies 

 on the cliff-faces 3 to 4 feet above ordinary high-tide level ; and on tlie sloping 

 cliffs behind the Needles, and at Casana on the east coast, it is often found 

 under the narrow fronds of Porphyra linearis. V. memnonia, is usually fertile 

 on the Howtli coasts, except when growing in deep shade, or at lower levels 

 than usual. 



On the south side of Balscadden Bay V. memnonia, V. prominula, and 

 Arthopyrenia halodyfes are associated, the reddish-brown spots of A. halodytes, 

 some of them nearly an inch in diameter, conspicuously variegating the dark 

 thallus of the Verrucarias. A. halodytes is found also amongst tlie V. maura 

 growtlis in cracks and fissures where spray lies, and on the sides and bottoms 

 of small rock-pools above ordinary high tide. On the top of the rocky 



