Mosses and Lichens 



branched and lobed. If the thallus is torn across and viewed 

 with a hand lens, the torn edge shows that the thallus is com- 

 posed of a layer of long, loose, white fibres (the medullary layer) 

 between thin but more substantial surface tissues (cortical layers). 

 Over the surface of the mat are scattered flat or saucer-shaped 

 disks (apothecia) generally brown with a thin margin. These 

 are numerous toward the centre. The apothecia have suggested 

 the generic name Parmelia from parma, a small round shield. 

 Many species have also a powdery appearance due to the bursting 

 of the surface to emit little bodies (soredia) which may grow 

 into lichens. 



Parmelia conspersa, (Ehrh.) Ach. See Colour Plate V. 



Habit and habitat. On rocks and stones; degenerate on dead 

 wood. 



Vegetative organs (thallus). Leaf-like, not gelatinous when 

 moist. Pale green or straw-coloured above, blackening below, 

 appressed, the margin sometimes ascendant; cartilaginous, mem- 

 branaceous, the lobes mostly rather narrow sub-linear and much 

 divided, smooth, not wrinkled, the centre often bearing little 

 stalked bodies with knobs (isidiophorous) . 



Fruiting organs (apothecia). Disks chestnut; margin (thai- 

 line exciple) entire. 



Spores. Ellipsoid, simple, colourless. 



Name. The specific name conspersa, besprinkled, refers to its 

 surface which looks as if sprinkled with little grains. 



Parmelia physodes, (L.) Ach. See Plate V. 



Habit and habitat. Common on dead limbs of pines and 

 hemlocks, lightly attached to its support. When it completely 

 encircles the smaller twigs the tree has a particularly attractive 

 appearance. 



Vegetative organs (thallus). Gray-green above with finely 

 cut, inflated lobes, usually overlapping; black beneath except at 

 the margins where it is smooth and brown. 



Fruiting organs (apothecia). Large shallow cups; reddish- 

 brown with entire margins. 



Name. The specific name physodes is from the Greek <f>vo-a, 

 bellows, and olB, like, and refers to the inflated character of the 

 lobes. 



NOTE : The illustration shows a variety (vittata) with the thallus 

 more narrowly dissected than in the species. 



82 



