476 PYEENOPSIDACEAE. 



Family 5. PYRENOPSIDACEAE. 



The three species of Pyrenopsidaceae are small plants, of a black or 

 blackish-green color, and gelatinous and soft when moist. They are con- 

 fined to calcareous rocks, and are of interest because they are local in 

 their distribution, evidentlj^ being exacting in their reciuirements. Psoro- 

 tichia hermudana Riddle, an endemic species, has a verrucose ("warty") 

 crustose thallus, broken into small patches. The species of Omphalaria 

 have a foliose thallus. 0. cubana Tuck, has the thallus radiately lobed, one 

 centimeter or less in diameter, and the surface rough and much wrinkled. 

 It has been found only at Castle Harbor in Bermuda, and elsewhere only 

 in Cuba. 0. lingulata Tuck, has very smooth, tongue-shaped lobes, usually 

 under five millimeters in length. It was collected by Prof. Farlow at 

 Walsingham in 1881, and in the same region by Dr. Britton in 1912. 



Family 6. COLLEMACEAE. 



These are also dark or lead-colored lichens of a gelatinous consistency 

 when moist. Collema bermudanum Tuck, and C. thamnodes Tuck, are 

 endemic species, forming compact cushions less than one centimeter high, 

 on the calcareous rocks at Walsingham. The former is foliose and bears 

 some resemblance externally to Omphalaria cubana^ but it is more divided 

 and the apothecia become larger and superficial. C. thamnodes is fruti- 

 cose, which will distinguish it from any of the other gelatinous lichens 

 except Leptogium tenuissimum, from which it differs in the granular 

 (isidiose) lobes.* Collema nigrescens (Huds.) Ach. and C. flaccidum 

 Ach. are quite different from the two preceding species. They are foliose 

 lichens of considerable size, growing on the trunks of trees. C. nigres- 

 cens has a radiately wrinkled thallus with numerous small apothecia, 

 measuring about one millimeter in diameter, and without any margin. In 

 C. flaccidum the thallus is less wrinkled and the apothecia are fewer and 

 about twice as large. 



The species of Leptogium are paler than those of Collema. L. 

 tenuissimum (Dicks.) Koerb. is, perhaps, the most interesting of the Ber- 

 muda species. It has a fruticose thallus, the minute, erect lobes being 

 crowded into a crust. It has been found growing on the ground at 

 Paynter^s Vale. The material is sterile and a jiriori we should not 

 expect this distinctly northern species to occur in Bermuda, but the 

 thalline characters agree so well that there is not much doubt about the 

 identity of the plant. From the point of view of distribution the next 

 species, Leptogiwm marginellum (Sw.) Mont., presents a striking con- 

 trast, as it is a tropical species characteristic of the AYest Indies and found 

 in the United States only in the tropical portions of the Gulf States. 

 Anyone who has once seen the abundant, minute, cup-shaped apothecia, 

 each with its coronal fringe of delicate lobules, will never have any diffi- 

 culty in recognizing the plant again. The third and last species of this 

 genus, Leptogium tremelloides (L. f.) S. F. Gray, is cosmopolitan in dis- 

 tribution and is one of the commonest lichens in Bermuda, growing on 

 trees of various kinds in many localities. It has a lead-colored thallus, 



* Collema thamnodes is known only from sterile specimens collected by Professor 

 W. G. Farlow in 1881. It is very desirable that the plant should be found again in 

 the hope of obtaining the fruit and thus completing our knowledge of the species. 



