Guide to the Lichens of the New York Area — Part 7 



G. G. Nearing 



Group 8. The Blister Lichens. Papery Lichens of small size 

 growing in rosette form with narrow branches and lobes, the parts 

 of a few species puffed or swollen. Color varies from gray to 

 brown, greenish and white. Fruits black, gray or dark brown, 

 often frosted with gray or white ; dull, not shining. Spores 2-celled, 

 brown or blackish. 



Physcia. All the species in Group 8 belong in the genus 

 Physcia, which here includes Anaptychia and Pyxine, as the differ- 

 ences on which these two genera are founded seem unimportant. 

 Blister Lichens resemble the smaller Shield Lichens (Cetraria and 

 Parmelia) of Group 5, from which they can usually be distin- 

 guished — easily by microscopic examination of the spores, those of 

 Physcia being dark colored when mature and plainly 2-celled, while 

 the Shield Lichens have colorless, undivided spores. Under the 

 hand lens the fruits of Physcia are dull, while those of most of the 

 Shield Lichens are somewhat shiny. The frosted or pruinose 

 appearance often seen on the fruit disks of Physcia is absent from 

 the Shield Lichens. Physcia fruits are usually black, slate-gray or 

 blackish brown, in contrast with the chestnut-brown, yellow-brown, 

 greenish, or rarely yellowish gray which prevail among the Shield 

 Lichens. The upper surface of the lobes and branches of Physcia 

 is dull, often powdery, and without any yellowish tint, though the 

 interior may be yellow. Shield Lichens on the other hand have 

 usually a somewhat shiny surface, especially on the tips, and many 

 are distinctly yellowish. These characters, taken together enable 

 the lichenist to separate the two important groups in the field. 

 Algal cells Protococcus. 



(Three more or less upright species of Physcia will be found 

 with the Stalked Lichens in Group 4.) 



Physcia sorediata. Spotted Blister Lichen 



Also called Pyxine sorediata. Found throughout the New York 

 area rather plentifully on tree bark, occasionally on rocks. It forms 

 rosettes up to 6 or 8 cm. across, which cling closely and cover their 

 area completely, leaving no considerable spaces between the parts, 



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