LICHENES. 



471 



University, visited Bermuda and collected about 20 species of lichens, 

 some of which were studied by Tuckerman. Between 1905 and 1914, col- 

 lections were made by Dr. and Mrs. N. L. Britton, Dr. F. J. Seaver, and 

 Messrs. Stewardson Brown and Paul Bisset, resulting in the finding of 65 

 species and varieties, of which 50 had not been previously reported. As a 

 result of these several collections, we now have a total of 85 species and 

 varieties of lichens known to occur in Bermuda. Ten of these species 

 are endemic. An enumeration of these lichens with descriptions of new 

 species and varieties was published in the Bulletin of the Torrey Botanical 

 Club for April, 1916. 



It is probable that continued search in the islands would reveal a few 

 additional species. But it does not seem likely that there are over 100 

 lichens in the flora. The small area of the islands, the so-called coral 

 formation, and the large proportion of cultivated land, all combine to 

 make the conditions unfavorable for any considerable development of 

 lichens. As a general rule, the higher foliose and fruticose lichens, being 

 more exposed on account of their looser connection with the substratum, 

 demand for their development more favorable conditions than do the less 

 exposed crustose forms. The proportion of 23 species of the former types 

 to 62 of the latter is interesting testimony as to the character of the 

 environment. Further evidence of this is afforded by the considerable 

 number of sterile or depauperate specimens. 



Given these conditions it will be of interest to see what lichens there 

 are occurring in Bermuda, and then to indicate briefly the geographical 

 affinities of the lichen-flora. The lichens will be taken up in systematic 

 order with brief notes as to the more easily recognizable characters. 



GENERAL SYSTEMATIC ACCOUNT. 

 Order 1. PYRENOCARPALES. 

 Family 1. VERRUCARIACEAE. 



The three species of this family grow on calcareous rocks, especially 

 along the shore.* The black perithecia are at first more or less immersed 

 in the rock, but when mature fall out leaving shallow pits. They play an 

 important part in the weathering of the rocks. Verrucaria rupestris 

 Schrad. is a cosmopolitan lichen, represented in Bermuda by two forms : 

 the typical form with very thin continuous thallus, of a grayish color; and 

 the var. ruderum DC. with a thicker thallus which is more or less cracked 

 and areolate; the spores are one-celled. The other two species are endemic, 

 and belong to the genus Thelidium, which is distinguished by having two- 

 celled spores. Both species were discovered by Professor W. G. Farlow. 

 and the first has been named in his honor. Thelidium Farloivi Riddle 



* It is to he understood that fill general and comparative statements in this 

 account of the lichens are intended to apply to the Bermuda species only. 



