THE SCHWENDENERIAN THEORY OF LICHENS. 39 
The capsule is at first a solid homogeneous mass of tissue; the 
differentiation of its interior begins with the formation of an inter- 
cellular space, which separates several layers of cells and forms 
the wall of the capsule ; but the wall remains attached above and 
below to the columella. 
The intercellular space is traversed by rows of cells which 
stretch across from the wall of the capsule the inner mass of tissue, 
and the outer layer of the cell wall is developed into a distinctly 
cuticled epiderm. 
The first two or three layers of the inner mass of tissue forms 
the spore-sac, while the third or fourth layer produces the mother 
cells of the spores, and this layer of cells is first of all distinguished 
by being densely filled with protoplasm in which lies a large cen- 
tral nucleus. 
The mother-cells of the spores, after isolation, float in the fluid 
contained in the spore-sac until they form the spores by repeated 
division. 
The inner large-celled tissue, which contains but little chloro- 
phyll, and is surrounded on all sides by the spore-sac, is distin- 
guished as the Columella. The spore-sac is ruptured by the casting 
off of the operculum, but the columella remains dried up, and in 
Polytrichum there remains also a layer of cells the Epiphragm, 
attached to the points of the teeth of the peristome, and covering 
the opening of the capsule. 
THE SCHWENDENERIAN THEORY OF LICHENS. 
Wire. the last few years the opinions of scientific men have 
been much divided upon the question of the true nature and 
character of Lichens, and, judging the subject to be one of interest 
to microscopists generally, we venture to ask our readers to devote 
with us a short time to its consideration. 
Until about the year 1869, Lichens were universally regarded as 
a distinct order of plants, occupying a position between Algze and 
Fungi, and constituting the class Zzchenes in the common classifica- 
tion. In 1869, however, Schwendener propounded the then 
startling théory that Lichens were not autonomous plants at all, 
but simply aggregations of discomycetous Fungi living as parasites 
upon Algze—represented by the gonidia of the compound organism. 
This theory has found many supporters, amongst the most eminent 
being Mons. de Bary, Max Rees, E. Bornet, and Treub. The 
foundations for the hypothesis are mainly the following. It has 
