478 PHYSCIACEAE. 



poorly represented there, only three species, that can be identified with 

 certainty, having been found, and these only in sterile specimens. Par- 

 melia tinctorum Despr. is distinct in the isidia (tubercles) growing on the 

 surface of the thallus. P. perlata (L.) Ach. and P. latissima cristifera 

 (Tayl.) Hue are more difficult to separate; the latter is generally whiter, 

 with broader lobes, and larger soredia. 



Family 10. USNEACEAE. 



In discussing the Thelotremaceae, certain striking gaps in the lichen- 

 flora of Bermuda were noted. In the family Usneaceae we find another 

 such case. The family, commonly abundant in all regions, has but a 

 single rejDresentative in Bermuda, Ramalina comjjlanata (Sw.) Ach. This 

 is, however, one of the commonest of Bermuda lichens, growing on the 

 branches of trees, and easily recognized by its much branched, tuberculate 

 thallus. 



Family 11. BUELLIACEAE. 



Buellia parasema (Ach.) Th. Fr. is a cosmopolitan lichen, which is 

 common in Bermuda, especially on the cedar; it has a crustose thallus, 

 which sometimes disappears almost entirely, and flat black apothecia with 

 a persistent black margin, this last character serving to distinguish it from 

 the next two species, in which the apothecia are, except when very young, 

 convex and marginle'ss. Buellia myriocarpa (DC.) Mudd and Einodina 

 insperata (Nyl.) Zahlbr. resemble each other in general appearance; in 

 the latter, however, the apothecia when moist are brown rather than black, 

 and the spores are of the peculiar type known as polar-bilocular. These 

 two species, although gTowing on bark like Buellia parasema, are compara- 

 tively rare. 



There have been collected from a roadside wall at Devonshire, speci- 

 mens of a small, chalky lichen, with a whitish subfoliose thallus and 

 radiate, confluent lobes. No fruit has been found, so the plant can not 

 be determined with certainty, but the thalline characters agree exactly 

 with those of Buellia canescens (Dicks.) DeNot., which is very common 

 on the same habitat in England. As the species is entirely unknown in 

 America, the interesting possibility suggests itself of this species having 

 been introduced into Bermuda from England. 



Family 12. CALOPLACACEAE. 



Blastema floridana (Tuck.) Zahlbr. is a minute, inconspicuous lichen. 

 It might be confused with Lecanora suhfusca, but the disk is commonly 

 darker, and the spores are two-celled. 



Family 13. PHYSCIACEAE. 



This family includes three species very common in Bermuda, and two 

 that are less known there. All have a grayish, foliose thallus, and may 

 grow on rocks as well as on trees. In the cosmopolitan Physcia stellaris 

 (L.) Nyl., the thallus has radiating, convex lobes, without soredia. P. 

 alba (Fee) Muell. Arg. is also without soredia, but has flat lobes. In the 

 other three species, the thallus is more or less sorediate (powdery). P. 

 crispa (Pers.) Nyl. has broad lobes, with the soredia confined to the 



