Fink: Classification of Lichens 
111 
species, some of whose individuals run part of their course in 
the parasitic relation with an alga, while others pass their whole 
life outside this relation, is*a lichen is a rather fine distinction that 
is doubtful at best and scarcely worth considering. But it seems 
more reasonable to say that all species that are better developed 
when they live with algae than when they do not are lichens. 
Zukal (151) published an account of the frequent occurrence 
of one of the Hypocreaceae with an alga which he thought to be 
Palmella botryoides. He named the fungus Epigloea bactrospora 
Zuk. The perithecia are semi-immersed in the algal colony, 
through which the hyphae ramify and are attached here and there 
to the algal cells. We have here a pyreno-lichen, belonging to a 
well known group of Pyrenomycetes. Hence its phylogeny seems 
certain enough, and it furnishes another point of approach of 
lichens to other well known fungi. The lichen is so little modi- 
fied that Zukal placed it near the genus, Barya, of the Hypocrea- 
ceae; but Zahlbruckner, in Engler and Prantl (145), has removed 
it from its natural position and has erected for it a lichen family, 
the Epigloeaceae. The alga is sometimes found free on mosses, 
and is in other instances attacked by the lichen. However, the 
occurrence of free algae growing with those of the same species 
attacked by lichens is known to be frequent, as will be proved 
later in this paper. 
Zukal (152) also published some interesting results in his 
paper entitled “ Halbflechten.” Some of these concern his mono- 
typic genus Pariiphrddria and the species Pariiphrddria heimerlii 
Zuk., found on the leaves of J linger mannias. The lichen gains 
entrance to these hepatics through the rhizoids, which it entwines 
and penetrates. It extends into the outer tissues of the stems and 
penetrates the leaves, some of which are finally killed. The 
apothecia usually occur on the leaves and most commonly at 
points where algal colonies of Gloeocapsa or of Palmella happen 
to be present. Here the lichen hyphae grow through the algal 
colonies in all directions, but do not penetrate into the algal cells. 
Microscopic squamules or granules are formed. Zukal consid- 
ered each of these a lichen thallus. Only a portion of the lichen 
penetrates into the algal colony ; but some parts of lichens are 
commonly external to the algal mass with which they grow, and 
