MUS CI. 
375 
the formation of spores, even when, as in Archidium^ it is subsequently supplanted 
by them ; a large part of the central tissue remains as the so-called Columella^ and 
it is at the circumference of this that the mother-cells of the spores are formed. 
The structure of the mature capsule, and especially the contrivances for dispersing 
the spores, are, however, so different in the various principal sections of Mosses 
that it will be better to consider them more closely separately, and the more so 
because by this means we shall at the same time arrive at the distinctive characters 
of the larger natural systematic groups. 
^In the mode of origin of the sporogonium there is, as might be expected, 
less variety. [The oospore is first of all clothed with a cell-wall, continues to grow 
considerably, and is then divided by a horizontal or slightly oblique wall {basal 
wall). The lower (Jiypobasal) of these two cells undergoes only one or two divisions, 
and, as in Jungermannieae, contributes but little to the formation of the embryo. 
The upper {epibasal) cell gives rise to the capsule and the seta : a two-sided apical 
cell is formed in it, by means of two oblique divisions.] Hofmeister asserts that in 
Bryum argenteuni the upper cell (that facing the neck of the archegonium) is divided 
once or twice by horizontal septa before the first oblique division, while in Phascum 
and Andrecea this oblique septum is formed immediately after the first horizontal one. 
The apical cell now forms two rows of segments by partition-walls inclined alter- 
nately, and these segments are next divided by radial vertical walls, followed by 
further numerous transverse divisions. By this process the young sporogonium is 
transformed into a multicellular body which is usually fusiform, the lower end not 
participating in the growth in length. A swelling of this lower end, such as usually 
occurs in Hepaticae, takes place also in certain cases such as Sphagnum, Archidium, 
and Phascum. The apex of the sporogonium now becomes inactive, and beneath it 
the capsule is formed as a spherical, ovoid, cylindrical, or frequently unsymmetrical 
swelling which originates, in the typical Mosses, only after the elongation of the 
fusiform or cylindrical sporogonium, and after the raising up of the calyptra. The 
internal differentiation of this mass of tissue, at first homogeneous, gives rise to 
the various tissues which compose the capsule of Mosses, and especially to the 
mother-cells of the spores which first of all become isolated and then divide so 
as to form four spores. The contents of the mother-cell begin to divide into 
completely across it ; it forms simply a trabecula between the outer and the inner wall, which splits 
into two lamella. Between these is the opening of the stoma. 
^ [The embryology of Mosses is treated of in the following works. Hofmeister, On the higher 
Cryptogamia, Ray Soc. 1862. — Schimper, Rech. anat. et physiol. sur les Mousses, 1848. — Kühn, 
Entwick. d. Andreseaceen, Bot. Mittheil, von Schenk und Luerssen, 1874 — Vouck, Entwick. d. Sporo- 
goniuras von Orthotrichum, Sitzber. d. Wien. Akad. 1876. — Leitgeb, Das Sporogon von Archidium, 
ibid. 1879. — Kienitz-Gerloff, Bot. Zeitg. 1878. It appears that the tissue of the sporogonium presents, 
at an early stage, a differentiation into an amphithecititn, from which the wall of the capsule and of 
the spore-sac are derived, and a central endothecium, corresponding to the future columella and 
sporogenous layer. Lcitgeb has however pointed out that in the Sphagnacese the sporogenous layer 
is probably derived from the amphithecium. It is of interest to note also that, as Goebel has 
pointed out, the spores of certain Vascular Cryptogams are developed, like those of Mosse^, from a 
layer of cells {archesporium), {vide infra, p. 388). The development of the spores from a layer of cells 
occurs also in the developing sporogonia of some Liverworts : it is distinct in Anthoceros, less so in 
the Jungermannieae, still less in the Marchantiese, and does not take place in Riccia.'] 
