118 LICHENS. [BOOK i. 



8. Lirella, is a linear shield, such as is found in Opegrapha, 



with a channel along its middle. 



9. Patellula ; an orbicular sessile shield, surrounded by a rim 

 which is part of itself, and not a production of the thal- 

 lus, as in Lecidea. D. C. 



10. Globulus ; a round deciduous shield, formed of the thallus, 

 and leaving a hollow when it falls off, as in Isidium. D. C. 



11. Pilidium ; an orbicular hemispherical shield, the outside 

 of which changes to powder, as in Calycium. D. C. 



12. Podetia; the stalk-like elongations of the thallus, which 

 support the fructification in Cenomyce. 



13. Scypha (oplarium, Neck.), is a cup-like dilation of the 

 podetium, bearing shields on its margin. 



14. Soredia (globuli, glomeruli], are heaps of powdery bodies 

 lying upon any part of the surface of the thallus. The 

 bodies of which the soredia are composed are called 

 conidia by Link, and propagula by others. 



15. Cystula, or Cistella ; a round closed apothecium, filled 

 with sporules, adhering to filaments which are arranged 

 like rays around a common centre, as in Spha3rophoron. 



16. Pulvinuli, are spongy excrescence-like bodies, sometimes 



rising from the thallus, and often resembling minute 

 trees, as in Parmelia glomulifera. Greville. 



17. Cyphella, are pale tubercle-like spots on the under surface 

 of the thallus, as in Sticta. Grev. 



18. Lacuna, are small hollows or pits on the upper surface 



of the thallus. Grev. 



19. Nucleus proligerus, is a distinct cartilaginous body coming 



out entire from the apothecia, and containing the repro- 

 ductive organs. Grev. 



20. Lamina prohgera, is a distinct body containing the repro- 



ductive organs, separating from the apothecia, often 

 very convex and variable in form, and mostly dissolving 

 into a gelatinous mass. Grev. 



21. Fibrillce, are the roots. 



22. Excipulus, is that part of the thallus which forms a rim 



and base to the shields. 



23. Nucleus, is the disc of the shield which contains the 

 sporidia and their cases. 



