ON LICHENOUS FRUCTIFICATION ON ALG, 29 
in Scytonema, Sirosiphon, Stigonema (mamillosum), that these 
genera and probably the whole of the Scytonemacee and 
Sirosiphonacee could be no longer properly accounted alge, 
but should be relegated with Ephebe to the lichens. 
But another and a different solution is put forward now-a- 
days by Professors de Bary and Schwendener, and those 
(Reess, Bornet, Treub, and others) who accept the new 
doctrine of the nature of lichens. It has, as is well known, 
been previously long supposed that, assuming the gonidia to 
be really organs of the lichens, these may here and there (and 
by no means unfrequently) become detached from the parent 
plant, and, under conditions unfavorable to their forming a 
new lichen, carry on an independent (probably abnormal) 
alga-like existence; and hence that many of the so-called 
unicellular and some of the filamentous algal growths, which 
may have been regarded as specifically distinct organisms, 
should really be expunged the list of independent plants. 
On the other hand, Schwendener and the new school hold 
that the “lichen-gonidia”’? are unicellular and filamentous 
alge which vegetate within the lchen-thallus as the service- 
able (assimilating) host plants of a. parasitic ascomycetous 
fungus, the “ lichen-hypha.” A resumé of the whole question 
of the views put forward and the arguments adduced so far 
as the discussion has reached, both for and against, I have 
recently endeavoured to bring together,’ and it is hence 
superfluous to attempt here to recapitulate the particulars 
and points of his hypothesis, except as bear upon the group 
immediately in question. 
In his able and interesting work on the “‘ Gonidia-forming 
Algal-types,’” and beginning with the “‘ Phycochromaceous”’ 
series (Nostochine, Nag.) Schwendener places the Sirosiphon- 
acee in the front rank. He justly observes they should begin 
the series, amongst the bluish-green filamentous forms, by 
reason of the well-expressed contradistinction offered by them 
between apex and base, also by reason of their being marked 
by a formation of true branches, as well as, in their higher 
representatives, showing an evident accession to their thick- 
ness by subsequent growth. Possessing these specialities, 
they at the same time, however, show an unmistakable affinity 
on the one hand to the Scytonemee and Rivulariee in the 
common possession of ‘‘heterocysts ” and an apical growth, 
and on the other to the Nostochacee, which, wanting apical 
growth, form a transition to the Oscillariea. 
1 Quart, Journal Mic. Science,’ vol. xiii, n.s., p. 217; also vol. xiv, p. 
115, in which places the references to the various authors are given. 
2 «Die Algentypen der Flechtengonidien,’ Basel, 1869, 
