103 



Though variable, Parmelia physodes has well marked dis- 

 tinguishing characters. The pulting of the tips, and to a certain 

 extent, of other parts, separates it from all other species of 

 Parmelia except P. vittata, P. colpodes and P. perlusa. Typical 

 P. vittata forks into long branches of uniform width, with tips 

 which do not broaden. P. colpodes has broad tips black and 

 roughened beneath instead of brown and shining. Near the tips 

 of P. pertusa are conspicuous small holes puncturing the lichen. 

 The Physcias, which often show swollen parts, usually form 

 more symmetrical rosettes of smaller size. P. stellaris and P. his- 

 pida, the ones most likely to cause confusion, are white beneath 

 and fruit abundantly. The brown tips curled upward distinguish 

 Parmelia physodes from all other similar lichens except P. vit- 

 tata, while those tips which have pale blue soredia mark it from 

 all but Physcia speciosa, which is not puffed, and is white be- 

 neath, with conspicuous white holdfasts. 



Parmelia vittata. Forked Shield Lichen. 



Also called P. physodes var. vittata. Similar to P. physodes in 

 most characters, but differing in some which are plainly evident. 

 The trunks and lobes are long and rather straight, of uniform 

 width, about 1 mm., while the tips, though puffed are not 

 broadened, and never sorediate. Branches fork at a wide angle. 

 The black under surface is deeply wrinkled. P. vittata may be 

 looked for on trees in the higher mountains, but is nowhere 

 plentiful. 



Fruits frequently large, occasionally 25 mm. in diameter, 

 brownish or greenish, wavy, with thin rim somewhat notched or 

 broken. They are lifted as much as 5 mm. high, like mushrooms, 

 and the under surface of the fruit, like that of the lichen, is often 

 black, wrinkled and pitted. Spores undivided, colorless, 4 to 6 

 by 4 to 5 microns. 



Though forms intermediate between P. physodes and P. vit- 

 tata do occur, the typical lichens differ so evidently that they 

 may usefully be considered separate species. Since the tips of P. 

 vittata do not break into blue soredia, other characters should be 

 noted, especially the long, straight branches with parallel edges, 

 and the habit of forking wide like the letter Y. No other local 

 lichen with puffed tips has this habit. (For comparisons see P. 

 physodes.) 



