INTRODUCTION. T 
larged archegonium breaks away transversely near its base, 
leaving the base as the vaginula, which surrounds the base of the 
young fruit; and the upper portion is carried up on its point to 
become the calyptra, which is afterwards burst by the expansion 
of the fruit on one side (calyptra dimidiata or cucullata), or it is 
divided more or less equally into laciniæ at its base (calyptra 
multifida, or, if much enlarged, mitriformis). The fruit, in its 
order of evolution, consists at first of a prolongation from the base 
of the interior of the archegonium, and remains short, or more 
frequently is continued by growth, apparently at its apex, and is 
there finally enlarged into a globular or oblong capsule or theca, 
which contains the sac or sporangium, in which the seeds are 
included around a columella which arises from its base. The spo- 
rangium occupies the whole of the upper portion, and often 
nearly the entire cavity, of the capsule; when it does not reach 
to the base, the lower portion of the capsule collapses, and is 
contracted into a collum or neck, and all that portion of the 
fruit which occupies the space between the collum and the va- 
ginula is named the seta or pedunculus. As the capsule ap- 
proaches maturity, it is most frequently more and more in- 
durated, and when ripe bursts irregularly, in the Musci Schisto- 
carpi, at its sides or ends or by longitudinal fissures in its upper 
part, the segments cohering at their apices—or, in the Musci 
Stegocarpi, by the transverse separation of its upper portion. This 
upper portion has then interposed between itself and the capsule 
proper a highly hygrometrie ring of cells (the annulus), which is 
either set free at the fall of the upper portion of the capsule or 
operculum, and falls off with it, or remains attached to the mouth of 
the capsule itself; or sometimes this organ is obsolete, and when 
the opereulum falls it carries with it the apex of the columella 
and exposes to view the peristome, consisting either, in the 
Elasmodontes, of a conical membrane composed of elongated nar- 
row cells and cleft into four equal divisions, or, in the Arthro- 
dontes, of a highly complex organ consisting of eight, sixteen, or 
thirty-two equal narrow teeth, which are composed of many wide 
short cells, and are very hygroscopic, opening or closing, as they 
are affected by the atmosphere, for the escape or retention of the 
spores. Each of these teeth is composed of three bands of cells, 
two external, and usually coloured, one internal, always hyaline: 
the external two are of a somewhat fleshy substance, frequently 
dotted or striate, and are placed side by side; they cohere to- 
