230 LICHENES. [hidiu 



c. Thallus shrubby, rounded, usually much branched, mostly erect. 



a. Solid. Apothecia globose, filled ivith black powder (cistula) or 



solid. 



FAM. XVI. SPHiEROPHORE.E. 



34. Isidium. Ach. Isidium. 



Thallus crustaceous, spreading, adnate, bearing solid, erect 

 branches (or podetia ?). Apothecia orbicular, convex, at length 

 subglobose, solid, terminal upon the podetia and more or less 

 sunk in the extremity, so as to leave a border of the substance 

 of the podetium. — Name, lag, a kind of coral, and s/bog,form f 

 from the resemblance of the podetia to some kind of coral or 

 coralline. — The situation of this genus is very doubtful ; for 

 the majority of the ramifications are so short and so combined 

 as almost to constitute a fiattish warted crust, while the portions 

 that bear the fructifications are considerably elongated. 1 



1. I. lutescens, Turn, and Borr. (yellowish Isidium); thallus 

 tartareous thin cracked into tumid areola? greyish with a filmy 

 zonate margin, podetia very abundant minute very short yel- 

 lowish almost concealing the thallus. Turn, and Borr. Lick. 

 Brit. p. 87. — Lepraria lutescens, Ach. Meth. — E.Bot t. 1529. — 

 Lepra lutescens, Hoffm. PI. Lick. p. 100. t. 23. f. 1, 2 — Lichen 

 lutescens, Hoffm. — Isidium phymatodes, f3. phragmeum, Ach. 

 Syn. p. 282. 



Trunks of large trees, but not common ; in Surrey, Sussex, Suffolk 

 and Essex. — I have followed the able authors of Lichenographia Brit. 

 in making this a species of Isidium .• though without the fructification 

 the plant appears to be altogether a Lepraria, and the apothecia have 

 neyer been found in Britain. 



2. I. coccodes, Ach. (granulated Isidium); thallus tartareous 

 thin cracked into somewhat tumid convex areolae greyish with 

 a filmy zonate border, podetia abundant some scattered and 

 some clustered in patches simple and branched of nearly the 

 same colour as the crust, apothecia brown immarginate. Turn, 

 and Borr. — Ach. Syn. p. 283. Turn, and Borr. Lick. Brit, 

 p. 89. — Lichen coccodes, Ach. Prodr. — E.Bot. t. 1511. — <3. phy- 

 matodes ; podetia white very confluent when branched. Turn, 

 and Borr. I. c. — Isidium phymatodes, Ach. Syn. p. 282. — 

 Lichen ferrugineus, Hoffm. Enum. p. 9. t. 2.f. 3. 



1 This genus has happily been illustrated by Messrs. Turner and Borrer, 

 (whose definitions of the species I have adopted,) and they give the following 

 generic character ; " Apothecium a solid, hardish globule, terminating a solid sub- 

 cylindrical papillulu (podetium), resembling a' proper peduncle and formed 

 from the substance of the thalhi;, sometimes also sessile on the crustaceous part 

 of the thallus, covered in its early stage with the epidermis of the plant, after- 

 wards naked, but always semi- immersed and never reflexed in its lower part." 



