38o ECOLOGY 



beginning with those furthest from the shore though within the influence of 

 the salt water: 



1. The Ramalina belt. 4. Verrucaria maura belt. 



2. The Orange belt. 5. The belt of Marine Verrucarias. 



3. Lichina Vegetation. 



(i) The Ramalina belt. In this belt there are two zones of lichen vege- 

 tation: those in the upper zone consist mainl)^ of barren plants oi Ramalina 

 siliquosa^, rather dark or glaucous in colour with much branched fronds 

 which are incurved at the tips (Fig. 122). They are beyond the direct action 

 of the waves. The lower zone consists also mainly of the same Ramalina, 

 the plants bearing straight, stiff, simple, or slightly branched fertile fronds- 

 of a pale-green or straw colour (Fig. 123). The pale colour may be partly 

 due to frequent splashings by sea-spray. 



Ramalina siliquosuni in both zones takes several distinct forms, according 

 to exposure to light, wind or spray, the effects of which are most marked in 

 the upper zone. The plants growing above the ordinary spray zone generally 

 form sward-like growths (Fig. 124); at the higher levels the sward growth 

 is replaced by isolated tufts with a smaller more amorphous thallus which 

 passes into a very small stunted condition. The latter form alone has 

 gained and retained a footing on the steep faces of the hard and close- 

 grained quartzite rocks. "On the western faces, indeed, it is the only visible 

 vegetation." The dwarfed tufts with lacerated fronds measuring from 

 i to I an inch in height are dotted all over the quartzites. On the sea faces 

 the plants are larger, but everywhere they are closely appressed to the rock 

 surface. At lower levels the fronds lengthen to more normal dimensions. 

 "On these steep rock-faces there is a complete absence of any of the 

 crustaceous species. The problem, therefore, as to how the Ramalina has 

 obtained a foothold on these very hard precipitous rocks, which are too 

 inhospitable even for crustaceous species is an interesting and puzzling one." 



In the Ramalina zone along with the dominant species there occur 

 occasional tufts ol R. Curnowii and R. subfarinacea, the latter more especially 

 in shady and rather moist situations. There are also numerous foliaceous 

 and crustaceous lichens mingling with the Ramalina vegetation (Fig. 125), 

 several Parmelias, Physcia aquila, Xanthoria parietina, Buellia canescens, 

 B. ryssolea, Lecanora atra, L. sordida, Rhizocarpon geographicum and others. 

 In the main these are arranged in the following order descending towards 

 the sea : 



1. Parmeliae. 3. Xanthoria parietina. 



2. Physcia aquila. 4. Crustaceous species. 



1 The two morphologically similar plants Ramalina cuspidata and R. scopulorum are here 

 united under the older name R. siliquosa. The distinction between the two is based on reaction 

 tests with potash, which give very uncertain results. 



