428 Dr. J. Miiller on the 
species, contain a simple series of green cells charged with 
chlorophyll, which touch each other at their ends, and are 
usually several times as long as broad. But the details stop 
here if we are working with an ordinary microscope; and it 
was by this means that Ehrenberg drew the analysis of his 
new genus. 
By a better method of analysis, and by the aid of very 
superior objectives, Dr. Karsten and Prof. Schwendener, in 
1862, ascertained that round the large confervoid filaments 
there exist others which are much more slender, about 1-2 p 
in diameter, which appear to be hyaline, and creep, as it were, 
over the surface of the large green filaments. ‘There is only 
a single series around the green filaments; and, moreover, 
this series is interrupted, the slender filaments not touching 
each other laterally in a regular manner ; but they often show 
anastomoses, and sometimes form here and there a very close 
network. Thenceforward we had in the thallus of the Ceno- 
gonia, as in the other Lichens, two constituent elements :— 
that of the large green cells still enclosed in their mother cell, 
corresponding to the gonidia; and that of the slender hyaline 
filaments, corresponding to the hyphoidal filaments. But 
no genetic connexion between the two had been observed as 
late as 1866 (De Bary, Morphol. und Physiol. der Pilze und 
Flechten, p. 270). 
It is therefore clear that, according to the celebrated theory | 
of Prof. Schwendener, put forward in 1867, the large green 
filaments would represent the nutritive alga, and the slender . 
hyphoidal filaments would be the parasitic fungus, the two 
forming together the thallus of a plant which, as a mixture, 
would no longer have its legitimate place in the series of the 
classes of plants. 
Along with this normal structure we sometimes find incom- 
plete individuals, in which the slender enveloping filaments 
are deficient, as in C. confervoides, Nyl., and others. In 
this case the plants are necessarily barren, without apothecia ; 
for these, according to the researches of Prof. Schwendener 
(Flor. Ratisb. 1862, tab. i.), are formed exclusively by 
means of the hyphoidal filaments. This difference, how- 
ever, is not absolute throughout; for the new Cenogonium 
pannosum (just published by me in the Flora de Ratisb. of 
the present year, Lichenol. Beitr. no. 309), which is a native 
of Brazil, and was sent by M. Puiggari, presents the two 
cases at once: certain filaments show only the large green 
tube, the gonidia; and others of the same clump, charged 
with apothecia, are surrounded by a small number of slender 
hyphoidal filaments. 
