240 



POPULAR HISTORY OF LICHENS. 



frequently confluent (several apothecia aggregated into 

 one) . 



Somewhat common on rocks and stones on our lowland 

 as well as highland hills, as on the Pentlands, near Edin- 

 burgh, and on Ben Lomond. It attains the summit of the 

 Alps, having been found by Saussure on the top of Mont 

 Blanc, and by Agassiz at a height of 12,850 feet on the 

 Jungfrau. Like various Urceolarias and Gyalectas it some- 

 times has an ochrey colour, derived from the peroxide of 

 iron in the substance on which it grows. 



b. Thallus leprose, granulose or pulverulent. 



6. Lecidea punctata (punctum, a prick or point). Thal- 

 lus glaucous or ash-grey, leprose or cartilaginous, sometimes 

 rimulose-areolate and rugulose. Apothecia black, sessile, 

 flat, with prominent thin margins, rarely convex, and im- 

 marginate. 



A very common corticolous species in lowland and sub- 

 alpine districts : it grows most frequently on the fir tribe, 

 on the oak, beech, and other trees, and on the wooden fences 

 of fields. On dead wood it sometimes occurs in a degenerate 

 form. In one of its commonest varieties, var. paramenia, the 

 crust is thin, equal, and bounded by the black hypothallus, 

 or effuse; the apothecia are largish, flat or convex. In 



