104 LICHENES. [Arthonia. 



usually scattered in rough, uneven, flattish, irregular, sub-confluent 

 portions, exhibiting the face of the rock on which it grows in the inter- 

 stices : sometimes the central portion of the thallus is continuous, 

 areolate, and of a very pale flesh colour, but the surface is more com- 

 monly whitish and powdery ; within, the thallus is of a pale greenish- 

 yellow : it is somewhat radiated towards the margin, which is unin- 

 terrupted all round, fibrous or silky, of a dusky olive-brown. The 

 surface is not altered when moistened. The verruca or receptacles 

 are subrotund, larger than rape seed, elevated, rather evenly scattered, 

 the larger nearer the centre : on their tops the lens discovers stellato- 

 radiate, pruinose gyrations, which are the disks of the apothecia ; the 

 lamina proligera is pale brown, pellucid, striated, but without any 

 distinct tegument, yet the disk is somewhat opaque. The apothecia 

 stand on the edges of vertical plates, which are opaque, dark brown, 

 or almost black, plunged in the white cortical matter of the verruca. 

 The cylindrical vessels that cause the lamina to appear vertically 

 striated often have their summits emerging above the disk. The la- 

 mina in old age drops off 7 , when the surface of the singular supports 

 remains black, and of the original figure of the apothecia. 



18. ARTHONIA, Ach. 



Thallus crustaceous or cartilagineo-membranaceous, uniform. 

 Apothecia roundish, elongated or varying in form, nearly 

 plane, not bordered, within somewhat gelatinous, covered by 

 a dark membrane. 



1. A. impolita, BORR. Thallus subtariareous, cracked, un- 

 even, greyish-white, indeterminate; apothecia immersed, flat, 

 somewhat confluent, brownish lead-coloured, pruinose. Borr. 

 in Eng. Bot. Supp. t. 2692, /. 1. 



On trees at Cledaneanure, County of Kerry. The surface of the 

 thallus is powdery : single apothecia rounded or oblong, with their 

 edges raised, and with a thallodal covering ; surrounding the apothecia 

 there are usually cracks of the thallus. 



2. A. lurida, ACH. "Thallus obsolete, continuous, smooth, 

 dull-lead-coloured or brownish ; apothecia sessile, roundish, 

 slightly convex, reddish-black." Borr. in Eng. Bot. Supp. t. 

 2692, / 2. 



On box, in a shaded grove, at Ardtully, County of Kerry. I have 

 given the specific character from English Botany, yet I confess I can- 

 not detect the thallus on my specimens ; on the contrary, the apothecia 

 plainly emerge from under the cuticle of the bark on which it grows, 

 indicating the habit of a Fungus ; and yet I have found cylindrical 

 bodies, acuminated at each end within the apothecia, corresponding to 

 Gongyli. 



3. A. Swartziana, ACH. Thallus membranaceous, thin, 

 whitish; apothecia roundish, repand, irregular, confluent ; their 

 disk, black, rough. Ach. Lick. Un. p. 142. Eng. Bot. t. 2079. 



On bark, near Belfast, Mr. Templeton ; Askew Wood, County of 

 Kerry. Varies in the colour of the thallus from whitish, through 

 cream-coloured and yellowish, to brownish, as in Mr. Templeton's spe- 



