Lichens, Genera and Species 



often covered with a white powder (pruinose), with numerous 

 pustular prolusions above and corresponding indentations below. 



Fruiting organs (apothecia). Somewhat shield-like. 



Name. The specific name pustulata is the Latin for "blistered" 

 and refers to the protusions on the thallus. 



Rock Tripe, Umbilicaria vellea, (L.) Nyl. See Colour Plate 

 XI. 



Habit and habitat. On rocks in high mountains. 



Vegetative organs (thallus}. Large, one-leaved, leathery and 

 somewhat smooth, ash-coloured with a bloom above; brownish 

 to black, and hairy, below. 



Fruiting organs (apothecia} Small, appressed, orbicular and 

 plaited, becoming convex. 



Name. From the Latin vellus, fleece, referring to the hairy 

 nature of the under surface. 



Umbilicaria Dillenii, Tuckerm. 



Habit and habitat. On rocks. 



Vegetative organs (thallus). Leaf-like, leathery, the largest 

 species known; brownish-green above, smooth and even; in- 

 tensely black below with crowded, short fibrils, attached only at 

 one point. 



Fruiting organs (apothecia}. Orbicular, convex, attached only 

 at the centre, the disk ridged concentrically. 



Name. Named in honour of the great botanist Dillenius. 



Umbilicaria Muhlenbergii, (Ach.) Tuckerm. See Colour 

 Plate XI. 



Habit and habitat. On rocks. 



Vegetative organs (thallus). Large, leathery to rigid, irregu- 

 larly pitted; olive-brown above, darker below. 



Fruiting organs (apothecia). Oblong and appressed, passing 

 into irregular, often star-like plaited clusters without a common 

 margin. 



Name. The specific name was given in honour of a Henry 

 H. Muhlenberg. 



Genus PELTIGERA, (Willd.) Fee. 



The Crescent-shield Lichen. The vegetative portion 

 (thallus} of the Genus Peltigera is leafy and often large; it is 

 veiny and rough, hairy beneath; the algal layer is blue-green, 

 excepting in two species (venosa and aphthosa). 



85 



