Is Pelvetia canaliculata a Lichen ? 
297 
place at a very early stage. Judging from the number of fungi 
which have been recorded on seaweeds (fungi which have, however, 
received little attention) such endophytic species are probably far 
from rare. 
In considering this special case, it may be well to give a recent 
definition of the class Lichenes as it is accepted by systematists. 1 
“ Lichenes (Flechten, Flechtenpilze), Ascomyceten und Basidiomy- 
ceten, welche mit Arten der Schizophyceae oder Chlorophyceae, 
namentlich der Protococcaceee und Pleurococcaceae derart verbun- 
den sind, dass sie auf den Algen entweder nur parasitisch 
vorkommen oder aber mit denselben eine innige Vereinigung, ein 
symbiotisches Konsortium, bilden, das eigenartige, bei den Pilzen 
nicht vorkomtnende Wachstums- und Lebenserscheinungen zeigt 
. . . . ” It is obvious that Pelvetia with its attendant fungus 
cannot enter into the class as thus defined. No lichen is known 
which has a brown algal gonidium. Further, there is in Pelvetia a 
definite and characteristic sexual reproduction, whereas the algae 
functioning as gonidia, have never been known to reproduce in any 
way but by cell-division, though some of the species when living 
free, reproduce by zoospores, etc. Moreover, the vegetative 
structure, as well as the reproductive, of the Pelvetia-Mycosphcerella 
complex is totally different from anything known in lichens. If the 
association be regarded as a lichen as the author suggests to what 
are we led ? The association would be the type of a new division 
of lichens and would rank as Phaeolichens. The gonidia of lichens 
are also free living plants and so can be placed in the algal families 
to which they belong. The Pelvetia-Mycosphcerella association is so 
close that the author has not yet found an uninfected alga and 
therefore on the assumption that “symbiosis” between alga and 
fungus implies a lichen, “ Pelvetia ” would have to be taken out of 
the Fucaceae, as it is never free-living—a reductio ad absurdum. 
It seems to us to be not a question of whether Pelvetia- 
Mycosphcerella is to he considered as a lichen but what relation 
exists between the two plants. If it be really a case of symbiosis, 
it seems to be more akin to mycorhizae, although the Ustilagineae 
with their eventual spore formation are at present more suggestive. 
No one has yet proposed forming special classes for mycorhizal 
phanerogams, pteridophytes or hepaticae even in those cases where 
the whole plant is permeated by a non-fruiting fungus as in 
Ericaceae, Loliuni, etc., and where the association seems to be an 
1 Erigler (-Gilg) Syllabus der Pflanzenfamilien, Editn. vii, p. 67 (1912). 
