298 A. Lorrain Smith andj. Ramsbottom. 
obligate one for the higher plant. The association under discussion, 
if symbiotic, appears to us to be of this kind and not one with the 
peculiar structural and physiological characteristics of lichens. It 
would be exceptionally interesting to find that there is an obligate 
symbiosis in this case (also in other species of the alga) and we 
hope that Mr. Sutherland’s further investigations will throw light 
on the point. 
It may be pointed out in conclusion that if the most recent 
“ biological ” definition of a lichen be adopted 1 —“ A lichen is a 
fungus which lives during all or part of its life in parasitic relation 
with the algal host and also sustains a relation with an organic or an 
inorganic substratum ”—then the association (or rather Mycos- 
phterella Pelvetice) is not a lichen. We ourselves are conservative 
enough to still hold to “ the assumption that the alga forms part of 
the lichen ” and do not seek any support for our contentions in such 
a confused definition. “Writers of text-books on plant morphology” 
may be interested to know that they “ have, with a few notable 
exceptions, signally failed to be consistent in their treatment of 
lichens ”—a statement which is upheld by the absurd assumption 
that the authors considered the lichen a fungus or an alga according 
to which name came first in their definition. In this short note we 
have necessarily left out of account much that might have thrown 
more light on the discussion such as the question of symbiosis in 
lichens including antagonistic- and para-symbiosis. The matters 
involved will be discussed fully in a forthcoming workon lichens now 
in preparation by one of us. 
' Fink B. “ The nature and classification of lichens, ii. The lichen 
and its algal host.” Mycologia, V, p. 97, 1913. 
