2 The Status of the Algo-Lichen Hypothesis. 
ens which, according to Johow, are made up of the hyphal ele^ 
ments of a hymenomyceteous fungus and an alga. Massee claims to- 
have discovered a Gasterolichen. So that now we have lichens: 
placed among the Ascomycetes and the Basidiomycetes, and by 
good authority. 
Wallroth (1825) was the first to make any study of the gonidia.. 
He was followed by Koerber (1839), who studied them more fully 
than did Wallroth. But not until 1851 was made anything like an ex- 
planation as to their probable origin and subsequent growth. This- 
was done by Bayrhoffer. He asserted that the gonidia came from 
the *' fibrous stratum, the fibres of which swelled at the top and 
produce male gonidia." Speerschneider, who was the next to study 
the gonidia, differed from Bayrhoffer on some points, but agreed as- 
to their probable origin. Schwendener, in his earlier works, took a 
similar view, basing his argument on the fact that the gonidia, 
many of them, seemed to be connected with the ends of the hyphae. 
De Bary, in his work of 1865, agreed with Schwendener as to the 
heteromerous lichens, but in case of such species as belong to the 
Collemaceae, etc., he said: ''Either the lichens in question are the 
perfectly developed states of plants whose imperfectly developed 
forms have hitherto stood among the algse as Nostocaceae and 
Chroococcete, or the Nostocacea? and Chroococceae are typical algae,, 
which assume the form of Collema, Ephehe, etc., through certain 
parasitic Ascomycetes penetrating into them, spreading their myce- 
lium into the continuously growing thallus and becoming attached 
to their phycochrome-containing cells." This gave to Schwendener 
the idea of dualism which he afterward formulated and presented 
to the world. Such was the beginning of the much-debated " Algo- 
Lichen hypothesis." Schwendener in this famous theory declares 
that all lichens, so-called, are dual organisms, consisting of a fungus, 
parasitic upon an alga, whole colonies of which it envelops with hyphse. 
These algae he divides into two classes, Phycochromacefe, or those 
with bluish-green coloring matter, phycochrome, and Chlorophyl- 
laceae, or those containing chlorophyll. The first of these he di- 
vides into five types : 1, Sirosiphoneae ; 2, Rivularieae ; 3, Scytone- 
meae ; 4, Nostocaceae ; 5, Chroococceae. The latter he separates 
into three types : 1, Confervaceie ; 2, Chroolepideas ; 3, Palmellaceae. 
To some one of these types, he claimed, the gonidia of every lichen 
could be referred. 
About this time Famentzin and Baranetzky by cultivating the 
gonidia of several lichens [Physcia [Theloschistes] parietina, etc.) 
