572 Lichenes. 



Knowles, M. C, The maritime and marine Lichens 

 o f H o w t h. (Sei. Proc. roy. Dublin Soc. XIV. (N. S.) 6. p. 79— 

 143. pl. 3—9. Map 1. 1913.) 



After an introduction oonsisting of a few remarks concerning 

 tides, wind, climate, moisture, that is the climatic conditions on a 

 large scale, the attempt is made to give an ecological account of 

 the lichens of Howth. 



Leaving aside the füll use of the terms "formation" and "asso- 

 ciation" except as a general heading, the authoress groups the lichens 

 Vegetation for purposes for description, into saxicolous, corticolous 

 and terricolous lichens. 



As regards the distribution the following Belts and Zones are 

 distinguished: 



A. The Lichens of the Rocky coast (Saxicolous lichens) 

 I. Silicious Rocks. 



1) The Ba malina-Belt. The i?ama/z>/«-Belt Stretches from the 

 high water mark of an ordinary spring tide to the top of the highest 

 cliffs and even further inland. The distinction of the characteristic 

 species of i?«iw^/ma-appears to be very difhcult, and the authoress 

 would make no difference between R. scopulonini sfnd R. cuspidata 

 which form the chief constituents of the belt for the purposes of 

 this paper. 



The lower Ramalina-zone is occasionally touched by spray from 

 the sea, and the plants are therefore washed free of dirt. The spe- 

 cimens are lighter in colour, and usually very fertile. The podetia 

 are upright, stiff, simple or slightly branched. The Upper Ramalma- 

 zone consists of plants darker in colour, much branched and usually 

 barren. The tips of the branches are incurved. The whole zone 

 offers a characteristic glaucous appearance. It is beyond the ordinary 

 spray zone. There exists in this belt an extensive foliaceous and 

 crustaceous liehen subvegetation, as long as light and air can reach 

 the subStratum between the Ra>nalina plants. Even in this sub- 

 vegetation a more or less distinct zonation can be made out. The 

 Parmelias occupy the light zone. Parmelia conspersa, Mougeotiij 

 prolixa and fuliginosa are the most typical maritime forms, whereas 

 P. perlata, saxatilis, omphalodes and physodes are more alpine in 

 character. On the Parmelias follow Physcia aqiiile and parietina, and 

 the various crustaceous lichens. Under shelter of the Ratnalina 

 plants, two mosses, Grimniia inaritiina and Weissia rupestris pene- 

 trate almost down to the sea. 



2) The Orange Belt. 



The orange colour is produced mainly by Physcia parietina, 

 Placodium rniivorum, tegulare and lohiilatuni. This latter species 

 may pas downwards into the Pelvetia canalicidata-zone , and we max 

 find the upper outrunners of the Vernicaria-maura-heXi here too. 



3) The Lieh in a Vegetation The upper limit of this coin- 

 cides with the upper limit of the Lichiyia plants. 



4) The V errucaria maura Belt. 



5) The Belt of Marine Verrucarias. The dominant species here 

 are V. microspora, striatula and mucosa, which mix with the alga 

 Hildehrandtia prototypus. 



II. Calcareous Rocks. No Ramalinas are found on these 

 rocks, there are few orange Lichens, and species of Verrucaria are 

 practically absent. Otherwise the rock is covered almost completeh'' 

 with Arthopyrenia foveolata (chiefly in the higher zones). 



B. Corticolous Lichens. 



