472 PYEENULACEAE. 



appears as a dark bluish-gray stain on the rocks, with the perithecia tend- 

 ing to be confluent in groups of two or more, and has spores measuring 

 18-20 X 7-9 micromillimeters ; T. bermudanum (Nyl.) Riddle has scarcely 

 any visible thallus, and the perithecia are smaller and scattered, and the 

 spores only 11-12 X 3.5-4.5 micromillimeters. 



Family 2. PYRENULACEAE. 



These lichens all grow on bark or dead wood. Porina nucula Ach., 

 growing on orange trees at Paynter's Vale, has a pale brown thallus and 

 rather prominent, globose perithecia of the same color, except for the 

 ostioles which are reddish. Porina tetracerae (Ach.) Muell. Arg., on 

 coffee trees at Walsingham, has a shining, olive-green thallus which makes 

 it conspicuous, and in this the perithecia are buried, with only the black 

 ostioles showing. Porina, phaea (Ach.) Muell. Arg. is quite different and 

 looks more like a fungus; its thin gray thallus is scarcely noticeable and 

 the innate perithecia are entirely black ; it has been found only at Harring- 

 ton House, where it grows on Juniperus. 



Pyrenula aurantiaca Fee is one of the most striking of tropical lichens, 

 its very smooth thallus forming orange patches of considerable size on the 

 bark of Rliizopliora, and entirely covering the perithecia. Pyrenula 

 brachysperma Muell. Arg. is a rare species collected at one locality on 

 Hall's Island, where it was growing on the bark of Eugenia axillaris; it 

 was previously known only from northern Brazil. In appearance this 

 species is very distinct ; the whitish thallus is very thin ; and the perithecia, 

 often confluent in twos, form conspicuous" black spots on the bark. The 

 species is also distinct in its two-celled spores. Pyrenula leucoplaca 

 (Wallr.) Koerb. has a very smooth white thallus, thicker than in the pre- 

 ceding species, and the minute perithecia are inconspicuous. It appears to 

 be common on various trees, having been collected in five different localities. 

 P. leucoplaca is well-known in northern regions, but its occurrence in 

 Bermuda is noteworthy. Another common and variable Pyrenula is P. 

 nitida nitidella (Flke.) Schaer., with a thallus varying from olivaceous to 

 brown, and with small perithecia. P. mamillana (Ach.) Trev. has a thallus 

 resembling that of the preceding species, but the perithecia are about twice 

 as large. 



Anthracothecium tetraspermum Riddle is an endemic species, found by 

 Mrs. Elizabeth G. Britton, growing on the trunk of a palmetto on Devon- 

 shire Marsh. It has an olivaceous thallus, which is rough and dull, instead 

 of smooth and shining as in Porina tetracerae. The specific name was 

 chosen on account of the brown, muriform spores being constantly four in 

 each ascus. The nearest relative of this species appears to be a plant of 

 the island of St. Thomas in the Antilles. 



Family 3. TRYPETHELIACEAE. 



This family, abundantly represented in tropical countries, has but two 

 species in Bermuda. Both grow on bark, and have the black perithecia 

 confluent in irregular patches: Melanotlieca aggregata (Fee) Muell. Arg. 

 has a thallus of a brownish tint, while M. cruenta (Mont.) Muell. Arg. is 

 a striking species sure to attract attention by its deep red thallus. 



