76 
NEW ARRANGEMENT OP 
Obs. Few mosses are more curious in the internal struc^ 
ture of the theca than Diphyscium. When a mature theca 
(from which we can alone expect to draw conclusions in 
any moss) is divided, we find a considerable space between 
the outer wall and the sporular sac, the intermediate pulpy 
matter having early dried up, and left nothing but " nu- 
merous whitish, branched, jointed succulent fibres" con- 
necting these two parts together. The pulpy substance 
above mentioned, seems, at an early stage, to have ex- 
tended in this moss considerably below the sporular bag, 
where it contained in its centre a small cylindrical pillar, 
which is left entire on the shrinking of the above substance, 
and acts as a supporter to the sporular bag, but is evidently 
of a different nature. A support of this kind seems pecu- 
liarly necessary both in this and the following genus, on 
account of the distance between the sporular sac and the 
wall of the theca. But it must not be understood, that we 
give this pillar or support to Diphyscium and Buxhaumia 
alone : on the contrary, we have now every reason to sus- 
pect that it is common to most mosses ; we have during this 
spring seen it in the junior state of Didymodon piirpureiirn^ 
but in none is it so beautiful as in Bryum ligidatum 
and Gymnostomum pyriforme ; of which last we regret 
that our plates were too much advanced in the engraver's 
hands to add dissections of this part. 
Within the sporular sac we have always found a colu- 
mella, formed as usual by the turning up of the sac, but 
fixed with it to the summit of the little pillar above men- 
tioned. The best mode of observing it, is to puncture a 
ripe sac, and by repeatedly plunging it in water, wash out 
the sporules ; the sac may then easily be drawn down or 
away from the columella, which appears almost equal in size 
to the sac. The columella is furnished at its summit with 
an opercular membrane, of a whitish colour, reaching and 
