MOSS DEVELOPMENT. 35 
The female organ, or archegonium, is flask-shaped, and accord- 
ing to Wurzburg, always arises in typical mosses from the apical 
cell of the shoot. It consists of a broad base supporting a roundish 
ovoid portion, above which rises a long, thin neck, generally twisted 
on its axis. The wall of the rounded portion consists of a double 
layer of cells, and passes up continuously into the wall of the neck, 
composed of a single layer of cells of from four to six rows. 
Together they enclose an axial row of cells, the lowest of which 
is ovoid, and produces the oosphere. When mature, the axial 
cells become mucilaginous, and force open the four uppermost or 
stigmatic cells of the neck, thus allowing the antherozoids to 
penetrate to the oosphere. Fig. 16. The conversion into muct- 
lage of the canal cells and the opening of the neck take place in 
the same manner in the Hepaticze or Liverworts. 
The fertilized oosphere results in the Sporogonium, which grows 
by elongation, and long before the formation of the spore capsule 
tears away from its base the ventral portion of the archegonium, 
forming the calyptra or hood; the neck of the archegonium as- 
sumes a deep red-brown colour, and for some time crowns the 
apex of the calyptra. The sporogonium of all mosses consists of 
a stalk (seta) and the spore capsule (Theca or Urn), but the 
former is very short in Sphagnum, Andrea, and Archidium ; longer 
in most other genera and with its base planted in the tissue of the 
stem, which after fertilization, grows luxuriantly beneath and 
around the archegonium, forming a sheathlike investment, the 
Vaginula. The unfertilized archegonia may frequently be seen on 
the exterior of the Vaginula, as only one archegonium is usually 
fertilized in the same receptacle. 
The capsule has in all Mosses a wall consisting of several layers 
of cells and a distinct epidermis, which sometimes possesses sto- 
mata of a peculiar character. The whole of the inner tissue is 
never used up in the formation of spores; a large part of the 
central tissue remains as a Columella, round which the mother cells 
of the spores are formed. 
The structure of the mature capsule, and especially the contriv- 
ances for dispersing the spores are different in the various principal 
sections of Mosses, and are the means by which we arrive at the 
distinctive characters of the larger natural systematic groups. The 
origin of the sporogonium does not afford any great variety. 
The oospore of the fertilized oosphere is first of all clothed with 
a cell wall; continues to grow considerably, and is then divided 
by a horizontal or slightly oblique wall. The lower of these two 
cells undergoes only one or two divisions, and contributes but little 
to the formation of the embryo. 
The upper gives rise to the capsule and the seta; a two-sided 
apical cell being formed in it by means of the oblique divisions. 
