THE BRYOLOGIST. 



Vol, V. March, 1902. No. 2. 



LICHENS-PHYSCIA. 



By Carolyn W. Harris. 

 (With Plate III.) 



While the Physcias are found in the Northern States they are more 

 abundant in the South, especially the higher and more beautiful forms. 

 They are quite generally distributed, having been collected in all parts of 

 Europe, and in Japan. 



The thallus varies from nearly crustaceous, through f oliaceous to f ruticose. 

 The foliaceous type resembles very closely the Parmelias, but the thallus is 

 thinner and clings more closely to the substratum. The lobes are not so 

 blunt and leaf-like, but are finely cut and delicate. In most species of Parme- 

 iia the under side of the thallus is shining, as if varnished, while in Physcia. 

 it is dull and pale. The color is usually gray, tinged with green. The 

 under side is pale, often white, but appearing in some species black on ac- 

 count of the thick mat of black rhizoids. Often the lobes of the thallus are 

 terminated by long, stiff cilia. Some species are rarely found in fruit but are 

 covered with whitish soredia upon the upper surface and along the turned 

 over margins of the lobes of the thallus. The apothecia are smaller than in 

 Parmelia and are almost sessile ; the margin entire or crenulate, the disk 

 round and dark in color. In Parmelia the disk is quite thin, in Physcia it is 

 thick. The thin paper-like thallus of many species renders them difficult to 

 collect satisfactorily from the tree trunks on which they are so generally 

 found. Some species grow on mossy rocks, and in damp weather are easily 

 detached. 



By the earlier lichenists the Physcias were combined with Parmelia; 

 while the thalli are much alike in general appearance, their spore characters, 

 are quite different, and on close observation their thalli will be found to 

 differ very much, both in appearance and habit of growth. The name, 

 Physcia, was given to this genus in 1824 by Fries, in allusion, it is said, to its 

 delicate thallus, the name being derived from a Greek word meaning breath 

 or wind. 



Physcia sPECiosA. (Wulf., Ach.) Nyl. (Plate III. 4). This is one of 

 the Physcias most generally found in the Eastern States, and is also one of 

 the prettiest, often forming complete, round, star-like mats of a delicate sil- 

 very green. The thallus is very thin and brittle, much branched, with ob- 

 tuse strap-shaped lobes, which have deep wavy margins. These are flat 

 with rolled over powdery margins, especially toward the centre. Beneath, 

 the thallus is white with fibrils of the same color. The apothecia are small, 

 almost sessile, with cup-shaped disk, the margin of which is entire when 

 young, crenulate and curved inward when older. P. speciosa is found on 

 trees, but more frequently on mossy shaded rocks. It grows close to the sub- 



The January Bryologist was issued January 7th, 1902. 



