ON THE LICHEN-GONIDIA QUESTION. 
269 
subject, and discusses seriatim the considerations adduced by 
Scbwendener in favour of bis hypothesis, are contained in his 
well-known “ Gfeschichte und Litteratur der Lichenologie,” iii. 
Bd. 1872. Those of Dr. Th. Fries are recorded in the intro- 
duction to his 6( Lichenographia Scandinavica,” 1871, pp. 4-8, 
though he does not enter very minutely into details. Dr. 
Muller has also made a short communication upon the subject 
in the 66 Flora,” 1872, p. 90, in which he declares the new 
theory to be impossible, and at the same time puts forth a 
hypothesis of his own, which he thinks would give a new and 
more natural interpretation to the researches of Schwendener. 
And not only have these lichenists entered the field to 
maintain the old and well-established theory, but other 
botanists, such as Professor Caspary, have also lent their 
valuable assistance. This latter distinguished botanist has 
made some valuable observations upon, and adduced very strong 
arguments against, the hypothesis in a paper “ Ueber die neuren 
Ansichten in Betreff der Flechten, wonach diese Schmarotzer 
seien,” in Schriften der Physik Oekon. Gresellschaft in Kcenigs- 
berg, 1872, Abth. ii. p. 18. 
To give, however, anything like a fair abstract of the several 
arguments used by these writers in the various memoirs and 
works now quoted, would of itself far exceed the limits of the 
present article. All, therefore, that we can attempt to do is 
simply to point out their bearing upon the leading principles 
of the Schwendenerian hypothesis, as originally propounded by 
the author, and subsequently further illustrated by Bornet and 
others. And, indeed, if these leading principles can be shown 
to be untenable, and to have no foundation in fact, then all the 
subsidiary points connected with them must necessarily lose all 
their force and meaning. The best method, probably, as it 
certainly is the most concise, of showing the invalidity of the 
theory under discussion, will be to review the two main con- 
siderations upon which the Schwendenerian theory is evidently 
founded, and which the celebrated author, in a more recent com- 
munication entitled “ Die Flechten als Parasiten der Algen ” in 
“Verhandl. der Naturf. Gresellschaft in Basel,” 1873, again puts 
prominently forward. Afterwards we shall notice any objec- 
tions of a different nature, which do not so directly come under 
either of these heads. The two main considerations referred 
to, which thus fall to be discussed are — 1st, the agreement of 
lichen-gonidia with algae ; and 2nd, the relation between the 
gonidia and the hyphae. 
With respect to the former point, Schwendener, as already 
quoted, asserts “ That the different gonidia-forms, as to struc- 
ture and manner of increase, correspond to parallel types of 
unicellular and filament ose algae Now there can be no ques- 
