THE BRYOLOGIST. 



Vol. IV. OcTOKER, 1901. No. 4. 



An index to the four volumes of The Brvoi.ocist is being prepared and 

 will be issued in cohnection with the January, 1902, number. It is suggested 

 that all having files complete their sets and bind with this Index in one vol- 

 ume. Hereafter each vear, of six numbers, will have its own Index. 



LICHENS— PARHELIA. 



Bv C.\ROi.YN W. Harris. 

 (With Plate VI.) 



The Parmelias are widely distributed, and the greater number are found 

 in North America. In the vicinity of Chilson Lake, Essex County, New 

 York, in the southeastern part of the Adirondacks. eighteen species have 

 been collected. No doubt as great a number could be found in other local- 

 ities. On old apple trees, as well as on many of the other trres. will be 

 found one of the commonest of the Parmelias, P. caperata. It grows in 

 large, round mats, of a light pea green color, with a wrinkled surface, which 

 is usually covered with soredia; it is rarely found in fruit. vSpecimens of P. 

 cap f rata are often found a foot in diameter. On the rocks will be found 

 another Farmelia which is very common, /-*. conspersa. Like P. caperata it 

 is a delicate green, but the thallus is smoother and clings closely to the 

 substratum. The apothecia, which are very common, are dark brown. 

 These two Parmelias are readily identihed and can be found in any country 

 place where there are trees, stone walls, and rocks. 



The thallus of the Parmelia is foliose, large, distinctly branched, and 

 lobed. It is held to the substratum by black rhizoids. The medullary layer 

 is composed, of long loose filaments, like tow, which give it a soft woolly 

 appearance. By breaking the thallus this can be seen with a good hand 

 lens. The outer, or cortical layer is thin. The apothecia are scattered, but 

 are usually more numerous at the centre. They are cup shaped, the disk 

 generally chestnut or brown and the margin thin. The species vary in habit 

 but are usually horizontal and leaf like. On many species are found soredia. 

 generally the color of the thallus; this varies from gray or brown tinged with 

 green to blue green and dark brown. In two or three species the thallus is 

 almost black. 



The Parmelias show the highest development of the thalline type. In 

 many specimens there is a continued marginal growth, while the centre 

 portion dies away. The name comes from Parma, meaning a buckler or 

 round shield, with a rim, in allusion to the appearance of the apothecia. 



'I'he July HRNOLoGIST was issued July gth, 1901. 



