LICHENS. 23 





characteristics. He calls the first tribe Idiothalami, 



such as have fruit clusters or apothecia, differing in 

 colour and substance from the rest of the plant : to this 

 tribe belong the Lecideas, Lecanoras, Gyrophoras, 



Endocarpons, and some others ; the second tribe he calls 

 Ccenothalami, such as have the apothecia £>«/•£ 7 ?/ formed 

 of substance of the t) hall us or leafy part of the lichen : to 

 this division belong the Peltideas, Borreras, and other of 

 the broad-frond ed families ; the third tribe he calls 

 Homothalami, such as have the apothecia entirely of the 

 same form and colour as the frond, and to this tribe 

 belong the Usneas, Alectorias, Eamalinias, etc.; and he 

 calls the fourth tribe Atlialami, whose apothecia are absent 

 and their fructification imperfectly understood, ranking 

 under this head the Opographae, 



The rocks about Granton, and those on the shores of 

 Arran and Ardrossan, furnished us with two small plants 

 which we feel puzzled whether to assign to the sea- weed 

 or the lichen group. Growing like a coating upon the 

 stone, their flattened branches closely interlacing, 

 blackened and crisp in the sunshine, they resemble minute 

 fuci in form and colour ; but their fruit was contained in 

 orbicular tubercles, which seemed rather to claim rela- 

 tionship with the apothecia of lichens. We could find 

 no gonidia grains, otherwise we should at once have 

 proclaimed the two minute rock dwellers to be true 

 lichens. These plants are called Lichinia, the larger 

 species, small as a Screw-moss, grow r s between tide marks, 

 and every flow turns its blackened fronds to a full olive 

 colour (L. pygmsea). The smaller species grows high 



