Lichens, Genera and Species 



Fruiting organ (apothecia) Shield-like (scutellceform) with 

 a pale disk. 



Name. The specific name barbata is the Latin for "bearded." 



The Hair-like Usnea, Usnea trichodea, Ach. 



Habit and habitat. On trees in long waving tufts. 



Vegetative organ (thallus). Pendulous, greatly elongated. 

 The few secondary branches are smooth, bearing numerous lax 

 fibrils of variable length, cross-section circular (terete). 



Fruiting organ (apothecia). Small, disk pale flesh-colour 

 with margin bearing very few fibrils. 



Name. The specific name trichodea is derived from the 

 Greek T/jt^oetS?)?, resembling hair, and refers to the thallus. 



Genus THELOCHISTES, Norm., emend. 



The thallus is leaf-like (foliaceous) or scale-like ; usually yellow, 

 appressed or sometimes ascending and scrub-like; the fruits 

 (apothecia) are yellow and shield-like (scutellceform). The spores 

 are colourless, ellipsoid, simple, or with the ends divided off by 

 partitions (polar-bilocular) the end spaces sometimes united by 

 a tube running through the middle space. 



The Yellow Wall-lichen, Thelochistes parietinus (L.) 

 Norm. (Xanthoria parietina) See Colour Plate II. 



Habit and habitat. On trees and rocks usually near bodies of 

 water. 



Vegetative organs (thallus). Leaf-like, pale yellow to orange 

 above, white below; loosely appressed to the surface on which 

 it grows, the margins sometimes ascendant, not gelatinous 

 when moist. 



Fruiting organs (apothecia). The disk orange, the margin 

 (thalline exciple) entire. 



Spores. Colourless, ellipsoid, polar-bilocular. 



Name. The specific name parietina, is from the Latin parie 

 (/-) 5, a wall, referring to its habit of growing on stone walls. 



Genus PARMELIA, (Ach.) De. Not. 



Parmelias usually grow as horizontal mats, gray, blue-green, 

 dark brown, or brown tinged with green. They are closely 

 attached by black rhizoids to rocks and trees and are distinctly 



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