130 THEKMUTIS. 



so-called fertile condition, was thus taken for an Alga infested by 

 a Fungus (Hepp. Flecht. Eur. n. 712). De Bary illustrated this 

 further, and proposed an alternative. Either the lichens now 

 before us are the fully developed, fructifying states of plants, 

 the less developed conditions of which ranked heretofore as 

 Nostodiacece, Ckroococcacece, etc., among the Algce, or the groups 

 last-named are typical Algce, which assume the form of Collema, 

 Ephebe, etc., in consequence of being penetrated by certain para- 

 sitical Ascomycetes, which spread their mycelial cells through, 

 and thus condition the growing thallus. (De Bary, Morph. & 

 PJiys. d. Pilze, etc., p. 291.) Schwendener's development of the 

 latter hypothesis (Die Algen-typen der Flechten-gonidien, 1869, 

 etc.) opened up an enquiry of deep interest, which yet neither 

 his own profound researches, nor the later ones of Bornet (Re- 

 cherches sur les gonidies, Ann. 5, 17, 1873) and Stahl (Beitr. z. 

 Entwickelungsgeschickte d. Flechten, 1877) were sufficient to de- 

 termine ; and the question remained an open one, till it was set- 

 tled, and in favour of the autonomy of the Lichens, by Minks 

 (Das Microgonidium, 1879). Sirosiphon, Kiitz., of which sev- 

 eral species are recognized here (Prof. W. G. Farlow), has lately 

 found a place in certain Lichen-catalogues with the authority 

 apparently of Dr. Nylander; but the group of Algce in question, 

 as constituted, is only hypothetically associable with Lichens ; 

 and the eminent author cited has not yet attempted to remove 



the difficulty of so associating it. Ephebella, Itzigs., also 



North American (Farlow) is still further removed from Lichens. 



[THERMUTIS, Fr., Born. 



Apothecia very small, biatorine. Spores ellipsoid, colour- 

 less. Spermatia oblong; on simple sterigmas. Thallus 

 slender filiform, densely tufted ; the gonimia constituting, at 

 the extremities, a single, central axis, which breaks up, in 

 the older parts, into transverse rings. 



T. belutina (Ach.) Fr. ; thallus of very slender, decumbent, 

 sub-simple, crisped, blackish-brown filaments intertangled into 

 close, velvety cushions; apothecia a little concave, pale brown, 

 with an obtuse margin. Spores roundish-ellipsoid, simple, "-^ 



mic." Th. Fr. Lich. Arct. p. 286. Koerb. Parerg. p. 450. 



Gonionema, Nyl. Syn. I, p. 88, t. I,/. 11. 



Rocks and stones, Europe ; but known to fruit only in the ex- 



