120 
Mycologia 
thallus of this Opegrapha, he noticed loosely felted hyphae within 
the periderm and upon the surface, the hyphae becoming scarce 
at the margin. Where these hyphae encounter free Trentepohlia 
filaments, they become attached to the algal cells. He found the 
same relationship between Trentepohlia and Pyrenula nitida 
(Weig.) Ach. and also recorded finding the Trentepohlia fila- 
ments from within the lichen thallus extending into external fila- 
ments, which produced zoospores while still attached to the lichen. 
He also found that the same alga produces zoospores within the 
thallus of Opegrapha varia Pers., and that the lichen hyphae are 
often attached to zodsporangia of the algal host. The same 
worker found the algal host of Pannaria nigra (Huds.) Nyl. 
extending into external filaments, which sometimes become free 
from the lichen. Like de Bary, he found Nostoc parasitized by 
Collema, but showing minute tubercles, often nearly cut off from 
the lichen. Some of these tubercles become free and form 
minute, non-parasitized Nostoc colonies, at first not over a half 
millimeter in diameter. Zukal found Palmella botryoides, both 
free and parasitized by the lichen, Epigloea bactrospora Zuk. 
Cunninghan (43) and Ward (138) both studied the relation- 
ship of Strigula to its algal host and to the leaves on which the 
lichen and its algal host grow together. Cunningham found that 
the lichen produces fruit only after parasitizing the alga, and that 
the alga forms zoospores, oogones and antherids only when free 
from the lichen. Ward found the leaves of Michelia fuscata, 
especially during the rainy season, to contain networks of branch- 
ing mycelia of Strigula complanata (Fee) Nyl. These mycelia 
are composed of brown, septate, branching hyphae, spread over 
the leaf-surface without haustorial attachment. They rise from 
oval, brown, two-celled ascospores, and often produce clusters of 
brown conidia. A Trentepohlia-V\ke alga also grows here and 
there on the leaves, and the algal groups are often overgrown by 
these mycelia, which produce the conidia where they come in 
contact with the algae. The hyphae gradually penetrate into the 
algal masses, destroy them, and in the meantime produce sperma- 
gones and later perithecia. The lichen sometimes parasitizes the 
alga while the latter is very young, and the algal host is soon 
