Mosses and Lichens 



Fruiting disks (apothecia). Not numerous, shield-like and 

 dark chestnut. 



Branches. Flattened, not hollow, rolled in on the margin 

 which is beset with a fringe of dark-coloured hairs 0.3 to 0.5 

 mm. long. 



Name. The specific name (Islandica) refers to the fact that 

 this lichen is very abundant in Iceland. 



Genus USNEA (Dill.) Ach. 



Thallus shrub-like (fruticulose) or pendulous, in cross-section 

 round or angular, grayish-green, to greenish-white, sometimes 

 straw-coloured ; the interior consisting of a central tough cord 



surrounded by a 

 cottony layer. 



The fruits (apo- 

 thecia) shield- 

 shaped (scutellce- 

 form), pale, with a 

 fibrillous margin, 

 spores more or less 

 ellipsoid, undivi- 

 ded, colourless. 



The name is de- 

 rived from achneh, 

 the Arabic for 

 lichen. 



The Bearded 

 Lichen, Usnea bar- 

 bat a, (L.) Fr. See 

 Colour Plate I, fron- 

 tispiece, also Plate 

 III. 



Habitat. On 

 trees, both living, 



Vertical section through 

 the thallus. 



Cross section through 

 the thallus. 



Usnea barbata. Fr. (x) central tough cord; () central tough 

 cord of radiating fibre; (m) cottony layer; (g) alga; (sa) radi- 

 ating fibre; (r) cortical layer; (j) apex of thallus. 



, 



Vegetative organs (thallus). Shrubby (fruticulose) often 

 pendulous, greenish, covered with numerous radiating fibrils of 

 the same colour; the interior tissue (medulla) consisting of a 

 central cord surrounded by a cottony layer. The branches are 

 circular (terete) in cross-section and are rough with papillae. 



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