518 DR LAUDER LINDSAY ON NEW LICHENICOLOUS MICRO-FUNGI. 



verruciform character. But in this case the degeneration appears to be quite 

 unconnected with the growth of the parasite, which equally affects the thallus 

 and apothecia, whether healthy or diseased, normal or deformed. The parasite 

 may be scattered; or closely aggregated, becoming confluent and maculaeform; 

 or it may be copiously studded over the apothecia, and sparingly on the thallus 

 of the same species, or vice versa, though the former arrangement is the more 

 common. Generally there is a marked contrast of colour between the parasite 

 and the whitish or greyish thallus, brownish or reddish disk of the apothecia, 

 which it so frequently affects. Necessarily the Torula is most conspicuous by 

 reason of this contrast, where the thallus and disk of the host are pale — whitish 

 in the one case, and brownish in the other. Its structure is essentially the same 

 on whatever lichen it be parasitic. In one case I found it occupying the cavity 

 of spermogonia (in Lecanora varia).* 



2. Genus Coniothecium. 



There are various points of resemblance between Coniothecium lichenicolum 

 and Torula lichenicola. In both cases the parasite is black, and is conspicuous 

 from contrast of its colour to that of the pale (or whitish) thallus on which it 

 so frequently occurs. In the Coniothecium the basal cellular tissue is the same. 

 There is no complete perithecium; the granular or powdery surface consists of the 

 free spores, which possess deep and dirty colours, mostly brown, though some- 

 times blackish or olive. In the young state only is the Coniothecium papillseform 

 or verrucarioid, in which condition it may be confounded externally with Torula, 

 or with the various organisms with which the Torula may itself be confounded. 

 But there is a greater number of points of difference between these two common 

 lichenicolous parasites. While Torula mostly affects corticolous lichens in the 

 fertile state, Coniothecium affects only saxicolous Lecanorce in the sterile, and 

 frequently isidioid or other degenerate or hypertrophic, condition. In maturity, 

 moreover, Coniothecium is much larger, and more conspicuous — visible for the 

 most part to the naked eye. It is largish and flattish, discoid or lecidioid, 

 resembling some forms of the pseudo-genus (of lichens) Spiloma, as well as the 

 parasitic Spilomatic fungi — Spilomium Graphideorum, and Gassicurtia silacea. 

 It varies considerably in size, surface, and outline ; in the old state frequently 

 resembling soot-spots. It is apt to be confounded with the apothecia, especially 

 when they are sub-degenerate, of various saxicolous Lecidew ; and the character 

 of the spores is sometimes such as to assist in this confusion. These spores are 

 typically, in the young state, spherical and single ; but they gradually acquire a 

 sub-cubical form, and are associated in groups — sometimes most irregular in out- 

 line — of two, three, or four, the form of the constituent spores then undergoing 



* Vide p. 520, and foot note f . 



