ON A Minute nostoc \vith spores, etc. 369 



so forth, througli certain parasitic Ascoinycetes peiietratiiicf 

 into tliem, spreading their mycelium into the continuously 

 growing thallus, and attached to their phycochronie- 

 containing cells." ^ The former of these hypotheses, as 

 is -well known, has many supporters, and, seemingly, a 

 considerable amount — at least, in certain instances — of evi- 

 dence in its favour. The latter hypothesis, on the other 

 hand, has found, if fewer, even more staunch adherents, most 

 prominent amongst whom are Schwendener and E,eess. 



Relinquishing the opinions supported by him in the earlier 

 portions of his elaborate memoir on the Lichen-thallus," 

 Schwendener, before he concludes, propounds the doctrine 

 that not only are the "Lichens'' in question (the Colle- 

 macese, alluded to by De Bary) no " Lichens," but that the 

 whole class, without exception, falls under the same category; 

 that is to say, that each is to be regarded as some one or 

 other Algal-type which has become, as it were, the home or 

 residence of a parasitic growth — the combination of the two 

 being, in point of fact, the so-called Lichen. His views 

 on the question the author has given more at large, in 

 relation to various types, in a subsequent memoir.^ These 

 he states generally thus : — " As the result of my researches 

 all these growths [Lichens] are not simple plants, not in- 

 dividuals in the ordinary sense of the word ; they are 

 rather colonies, which consist of hundreds and thousands of 

 individuals, of which, however, one alone plays the master, 

 while the rest, in perpetual captivity, prepare the nutriment 

 for themselves and their master. This master is a fungus of 

 the class of Ascomycetes, a parasite w'hich is accustomed to 

 live upon others' work ; its slaves are green algse, Avhich it 

 has sought out, or indeed caught hold of, and compelled into 

 its service. It surrounds them, as a spider its prey, with a 

 fibrous net of narrow meshes, which is gradually converted 

 into an impenetrable covering ; but, whilst the spider sucks 

 its prey and leaves it lying dead, the fungus incites the algse 

 found in its net to more rapid activity — nay, to more vigorous 

 increase. ... If this mode of illustration be permissible, this 

 fungus forms a remarkable contrast, not only to the predatory 

 and murderous spider, but, in quite an analogous way, to the 

 vine and potato-fungus, as well as all other fungi which 

 vegetate in living organisms, and destroy their host-plant, or 



' Professor A. de Bary, " Morpliologie u. phys d. Bilze, Flechten und 

 Myxomyceten," in Hofmeister's 'llaudbuch der Phys. Bot.,' Bd. ii, p. 291. 



- Dr. S. Schwendeuer, " Uutersuchungen ueber den Elechten-tliallus," 

 in Prof. Niigeli's 'Beitrjige zur Wissenscb. Botanik/ Hft. 4, p. 195 (1868). 



^ Dr. S. Schwendener, ' Die Algentypen der Plechtengonidien,' Basel, 

 1869. 



VOL. XII. NEW SER. D D 



