14 4 Proceedings of the Royal Irish Academy. 



branches. The boulders near the shore were gay with the yellow Physcia 

 parietina or Lecanora lobidata. Further away the rocks were covered with 

 great white patches of Lecanora parella, with its large, crowded apotheeia: and 

 Lecanora atra, with a grey, irregular crust and outstanding black fruits, was 

 very noticeable and very abundant. Further inland still, these two dominant 

 species were partly replaced byLecidea rivulosa, with its thick crust of varying 

 shades of purplish brown. Mr. TTattam also reports from A chill that " this 

 is undoubtedly the most common of all rock-lichens. It occurred on every 

 mountain-range and wayside boulder, both at high and low altitudes, and 

 makes perfect maps of varied brown hues intersected with black hypothallus." 

 Some of the patches observed by him measured 9 feet by 3 feet. Other 

 Lecideae, such as L. contigua and L. confiuens. with stout, black fruits, occurred 

 not seldom : and mingling with these more massive forms were species of 

 Bhizocarpon and Buellia in varying mosaics of green, grey, or brown : and 

 everywhere, though inconspicuous, the thin crust and small iron-red fruits 

 of Lecanora ferruginea. Species with bright brown thallus were not frequent, 

 but we secured specimens of Lecanora ZHcksonii and Bhizocarpon Oederi, both 

 of a yellowish red hue, and on the stones of a stream the equally bright 

 Lecanora lacv.stris. 



On many of the boulders the crustaceous forms were shouldered aside by 

 the leafy Parmeliae, the most common of all Parmelia saxatilis, with its lovely 

 grey thallus seamed and scored by innumerable zigzag white bines, and 

 often rough with small projecting points called "isidia" — outgrowths from the 

 thallus, which break away and form the beginnings of new growths. Almost 

 imperceptibly P. saxatilis passes over to the allied species P. omphalodes, a 

 darker plant, with a smooth shining thallus. Another Parmelia found in large 

 sheets is P. perlata, the curled edges of its thallus bordered with white pearly 

 soredia. P. caperata, though less abundant, helped to cover the boulders with 

 its yellowish green wrinkled thallus. On the same rocks, bristling tufts of 

 Ramalina pushed up between the Parnielia lobes. Other boulders were taken 

 possession of by the thick warted crusts of grey Pertusariae, many of them 

 sterile forms impossible to determine accurately. 



In the limestone districts of "vTestport and Castlebar the stone walls were 

 adorned with the brilliant yellow Lecanora murdrum and L. caUopisma, and 

 spotted all along with the milk-white thallus of L. calcarea, or the dark 

 brown patches of Verruca ria nigrescens. The outcropping rocks were 

 dotted with pin-holes, each one the seat of Verruearia calciseda, while here 

 and there the white surface was blackened with the crust of Pannularia 

 nigra. 



Among tree-licheus, the largest number belonged to various Graphideae 



