446 DR. LAUDER LINDSAY ON THE 



The apothecia of Abrothallus Usnece'm. Rabenhorst's specimen are frequently, 

 especially towards the base of the thallus, isolated, large, and epithalline ; con- 

 vex, Biatorine, immarginate; of a blackish-brown colour; and having all the 

 aspect of the usual apothecia of A. Smithii. Frequently, also, they become 

 aggregated, confluent, and difform, then assuming the aspect of species of 

 Phacopsis* (e.g., P. imlpina). Another — the most rudimentary, and a sterile, 

 probably a protothalline, condition of the plant — occurs in the form of maculae — 

 most irregular in form, size, and position ; sometimes raised or convex ; occupying 

 occasionally such exceptional sites as the under surface of the apothecia, or the 

 tips of the ultimate thalline ramuscles ; in the flatter case, giving the appearance 

 of Cetrarioid spermogones. Between the large, isolated, sporiferous, Biatorine 

 tubercles, and the aggregated or confluent sterile maculae, there is every gradation 

 of character. Of the isolated fertile apothecia, forms occur, which, though 

 generally rounded or sub- spherical, are sometimes conoid or flat and wart-like, 

 sub-immersed and emergent ; sometimes girt with a thick distinct thalline border. 

 The aggregate or confluent conditions, which are less frequently found fertile, 

 generally produce irregular one-sided swellings of the branchlets, or apothecial 

 cilia, on which also they find a site. Very seldom do they, in any of their con- 

 ditions, surround the branchlet or fibril, being almost invariably seated only on 

 one side thereof, producing angularities, swellings, and other deformities. 

 Occasionally they are sub-terminal clusters of tubercles ; in this, and in all other 

 cases, of a blackish-brown colour, which, under moisture, becomes a pure, though 

 dark, brown. The flattened disk passes gradually into the macula, frequently 

 becoming stellate or irregular in outline. 



The structure and contents of the hymenium must be examined in the 

 isolated, large, regular, Biatorine apothecia. The aggregated, confluent, and 

 difform conditions are almost invariably degenerate and sterile. The whole 

 hymenium is generally obscured by more or less abundance of brown granular 

 colouring matter ; sometimes, however, it is very free from this colouring matter, 

 and in such cases the thecre and spores are very distinct, though the paraphyses 

 are always indistinct, delicate, and obscured by much dark brown granular 

 colouring matter about their tips. The thecw are generally indistinct ; 8-spored ; 

 the spores generally arranged in two rows ; -0018'' long, -00045'' broad ; giving no 

 reaction with iodine. The spores are plentiful and distinct; oblong-ellipsoid; 



* Contrast with the genera Phymatopsis and Celidium this genus Phacopsis, Tul. " Mem. Lich." 

 p. 124 (name from <&uxbt, a nasvus or lentigo, a skin-wart) ; and especially the species P. vulpina, 

 Tul. (p. 126), Linds. " Mem. Spermog." plate iv. fig. 22, p. 125; Hepp exs. 474. Than this species no 

 Ziehen could more resemble, in its external aspect and habit of growth, a Fungus ; but no Lichen 

 gives, at the same time, a more distinct and beautiful blue or violet colour (varying in shade, and 

 sometimes very pale) with iodine (thecae and sometimes hymenium). While in Phymatopsis (Abro- 

 thallus) and Celidium the apothecia or groups of perithecia are essentially brown (though frequently 

 of a dark blackish-brown), in Phacopsis they are essentially black ab initio. 



