Mosses and Lichens 



Genus PHYSCIA, Fries. 



The vegetative portion (thallus) of the Genus Physcia is leaf 

 like, star-like, or sometimes with narrowly linear divisions, 

 beneath it has usual fibres of varying length; the generic name 

 is from the Greek <j>v<rtcr), a blister, evidently referring to the 

 inflated appearance of the thallus in some species. 



The fruiting portion (apothecia) are shield-shaped, with the 

 surface often covered with a whitish powder: 



The spores are elliptical, brown, two-celled in our species. 



Physcia leucomela, (L.) Michx. See Colour Plate VIII. 



Habit and habitat. On trees, most common southward. 



Vegetative organs (thallus). Ascendant and elongated, 

 mostly smooth, often narrowly linear, the densely entangled 

 lobes irregularly divided; beneath white, the margins beset with 

 strong, branched blackish fibrils. 



Fruiting organs (apothecia). Medium-sized, on short pedi- 

 cels, the disk white, powdery, the border lobed; the spores are 

 bilocular. 



Name. From the Greek \eu/co<?, white, and /*A,a?, black, 

 referring to the strong contrast between fibrils and surface. 



Genus UMBILICARIA, Hoffm. 



Thallus horizontal, leaf-like (foliaceous), scarcely divided, 

 leathery; either smooth or fibrillose beneath, attached to its 

 support by a single point. 



Fruits (apothecia) black, round, convex or sometimes irregular 

 in outline. 



Spores somewhat coloured, ellipsoid, either without cross- 

 walls or with both horizontal and vertical walls. 



The generic name is from the Latin umbilicus, a navel, referring 

 to the single point at which the thallus is attached to its support. 



The Blistered Umbilicaria, Umbilicaria pustulata, (L.) 

 Hoffm. 



Habit and habitat. On rocks in dry localities. 



Vegetative, organs (thallus). Horizontal and leaf-like, carti- 

 laginous; ash-coloured above, whitish toward the centre, 

 pale brownish or ash- coloured below ; smooth on both surfaces, 



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