Usnea.] LICHENES. 85 



in all its branches, without any appearance of buds or soredia, and 

 the apothecia when aged remarkably convex, wrinkled, and of a pur- 

 plish-brown. 



3. R. fastigiata, ACH. Tliallus erect, somewhat compressed, 

 smooth, laeunose, whitish-glaucous, the branches thickened up- 

 wards, fastigiate ; apothecia terminal, sessile, at length plane or 

 convex. Ach. L. Un. p. 603. Eng. Bot. t. 890. 



On trunks of trees ; frequent. On stones at the sea-side, Derriquin, 

 County of Kerry. The variety termed calicaris by Hudson has the 

 branches linear and acuminate, bearing sometimes short spur-like 

 lacinice. 



4. R. scopulorum, ACH. Thallus compressed greenish-white, 

 or greyish-brown, somewhat polished, sublacunose, the branches 

 linear attenuated ; apofhecia scattered, sessile. Ach. L. Un. p. 604, 

 E. Bot. t. 688. 



On maritime rocks near Howth ; Mr. Templeton. Our Irish plant 

 differs from that collected by Dr. Greville, in the Isle of Bute, with 

 which he has obliged me, by the broader thallus, which is more brown, 

 and, when aged, rough with oblong pale buds, that have each a pit 

 on their summits, scattered over the surface ; the disk, too, is less 

 coloured. 



5. R, farinacea, ACH. Thallus erect, pale glaucous-grey, 

 subcompressed, sublacunose, the buds (soredia) round, margi- 

 nated by the thallus ; the branches attenuated ; apothecia scat- 

 tered, on short stalks, of a pale buff. Ach. L. Un. p. 606. Eng. 

 Bot. t. 889. 



On trees ; near Belfast, Mr. Templeton. A variety occurs at Dun- 

 kerron, with the disk quite concolorous with the thallus, without any 

 shade of the buff colour. The segments of fertile fronds are wider 

 than the others. 



6. R. pollinaria, ACH. Thallus submembranaceous, smooth, 

 pitted, greenish-grey, branched, laciniated, buds (or soredia ) 

 roundish, marginate, or elongate and marginal, consisting of a 

 grey ish- glaucous powder ; apothecia nearly terminal, at length 

 dilated and margined. Ack.L. Un.p. 608. Eng. Bot. t. 1607. 



On trees ; near Belfast, Mr. Templeton. 



b. Thallus cylindrical. 

 10. USNEA, Ack. 



Thallus cartilagineo-crustaceous, cylindrical, hollow, enclosing 

 a central thread. Apothecia orbiculate, entirely formed of the 

 thallus, and of the same colour. 



The central thread is tougher than the enclosing cylindrical thallus ; 

 this, cracking transversely into elongated beads, sometimes gives 

 origin to an articulate variety. The buds (or soredia) arise on the 

 stem and main branches as minute white points, enlarge, break at the 

 top, and disclose a cancellated base ; the cells contain a powder which 

 developes young acuminate cylindrical shoots. The accident of more 



