LECIDEA. 



239 



on all our Highland mountains and in many localities in 

 lowland and subalpine regions. Around Perth it abounds 

 on old walls, built of boulders from the neighbouring Gram- 

 pians. It frequently grows on pure milky quartz, and is 

 then from the contrast of its blackish-green colour a very 

 pretty object. Its spores are somewhat large, oval or ob- 

 long, marked by irregular bulgings, dark-brown, and contain 

 generally four oblong rounded cells, which give the spores 

 an obscurely triseptate character ; they vary much in form 

 and size, are generally so dark in colour as to be indistinct 

 in their structure, but resemble in characters the spores of 

 certain Verrucarias. This species occurs abundantly in the 

 Arctic and Antarctic regions, and it is the last form of 

 vegetable life which has been met with by travellers on the 

 greatest elevations hitherto reached on the Andes and Hima- 

 layas. 



*** Thallus uniform, simple. 

 a. Apothecia black or blackish-red. 

 t Thallus tartareous. 

 5. Lecidea confluens (confluo, to flow or run together). 

 Thallus smoke-coloured or grey-whitish, very slightly rimu- 

 lose-areolate. Apothecia very black, naked, never greyish- 

 pruinose, appressed, flat, thinly margined, rarely convex, 



