AMERICAN NATURALIST. 
JANUARY, 1889. 
THE STATUS OF THE ALGO-LICHEN HYPOTHESIS. 
BY THOMAS A. WILLIAMS. 
TN treating this subject it will not be out of place to give first a 
^ short history of the growth of knowledge concerning lichens 
and their structure. The earlier lichenologists knew but very little 
of lichens as now understood, and comparatively nothing as to their 
internal structures. As the magnifying power of microscopes was in- 
creased, so the knowledge of the lichen thallus was increased. Tlie 
affinities of lichens to the discomycetous fungi on the one hand and 
to the algae on the other were early noticed and commented upon, 
and some species have been alternately placed among the fungi, 
then among the lichens, and others have been repeatedly changed 
from lichens to alga^, and vice versa. Later authors, as Comu and 
Tulasne, consider the lichen very near if not belonging to the As- 
comycetes. while De Bary, Krabbe, and others place them among 
the Ascomycetes without any doubt as to that being the proper place 
for them.^ Lately Cora and several other genera have been placed 
among the lichens under the name of Hymenolichens — i.e., lich- 
1 Stahl found the reproductory organs of CoUema to be very similar to 
those of the Dlscomycetes.' Borzi confirmed Stahl's observations by his 
own. Funfstiick, after a sj:udy of the development of the apothecia of Pel- 
tigera and Nephroma, believed that " the reproduction is by apogamy, 
with rudimentary sexual organs, as in Podospheera among the Discomy- 
cetes." De Bary says (Morph. and Biol, of Fungi, etc.): "The formation 
of the perithecia of lichens from the primordial coils of hypha? follows in 
general the same course as that of Xylaria, Polystigma, etc." This is con- 
firmed by the observations of Krabbe, Fijisting, and others who have made 
an extended study of the Cladoniae, Sphyri'dium, Lecanora, Lecidea, etc 
