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MUSCINEM. 
arises in exactly the place in which a branch would otherwise be formed, 
z. e. from the segment of the axis which lies beneath the cathodal half of the 
leaf; the antheridia may in this case be considered as metamorphosed branches. 
In Foniinalis, on the other hand, their morphological significance varies within 
the same receptacle ; the one first formed is the immediate prolongation of 
the axis of the shoot, arising from its apical cell; the succeeding ones are 
developed from its last normal segments, and therefore resemble leaves in 
their origin and position ; the last antheridia, finally, exhibit the morphological 
characters of trichomes, both in their variable number, their development as cells 
of the epidermis, and the want of definiteness in their place of origin. According 
to Kühn, AndrecEa behaves in precisely the same way as Fontinalis. The mother-cell 
of the antheridium of Fontinalis is constituted as an apical cell forming two 
alternating rows of segments; in forming the oldest and terminal antheridium 
the apical cell changes from a triseriate to a biseriate segmentation. These seg- 
ments are next divided by tangential* walls in such a manner that the transverse 
section (which meets two segments) of the young organ shows four outer and 
two inner cells; the wall of the antheridium, one cell in thickness, arises from 
the former by further division ; the small-celled tissue which produces the anther- 
ozoids from the latter. Andreaa behaves also very similarly in these respects; the 
primary mother-cell of the antheridium appears as a papilla and is cut off by a 
septum ; the lower cell produces a cushion-like support ; the upper cell is again 
divided by a septum into a lower cell from the divisions of which the tissue of 
the stalk is formed, and an upper cell out of which the body of the antheridium 
arises ; the formation of the latter takes place in the same manner as in Fontinalis, 
In Sphagnum the long stalk originates by transverse divisions of the growing 
papilla which produces the antheridium, the segments dividing again in a cruciform 
manner. The terminal cell then swells, and becomes divided by oblique walls of 
somewhat irregular position ; a tissue is thus formed, which, at a subsequent period, 
consists also of a wall formed of a single layer of cells and an inner very small-celled 
tissue which produces the antherozoids. 
The Aj^chegonimn consists when mature of a massive, moderately long base, 
which supports a roundish ovoid ventral portion ; above this rises a long thin neck, 
generally twisted on its axis. The wall of the ventral portion, which consists, even 
before fertilisation, of a double layer of cells, passes up continuously into the wall of 
the neck consisting of a single layer of cells formed of from 4 to 6 rows (Fig. 256). 
Together they enclose an axial row of cells, the lowest of which, ovoid and lying 
in the ventral portion, produces the oosphere and the ventral canal-cell, the upper 
cells being the canal-cells of the neck. These and the ventral canal-cell become 
mucilaginous before fertilisation. This mucilage forces the four uppermost cells 
(stigmatic cells) of the neck apart, and thus opens the canal of the neck, allowing 
the antherozoids to penetrate to the oosphere. Fig. 256, B, shows the row of 
canal-cells at the period when disorganisation is beginning, and when the stigmatic 
cells of the neck are still closed. In reference to the morphological significance 
of the archegonia, Leitgeb has already shown that at least the first archegonium 
of Sphagnum arises immediately from the apical cell of the female shoot; more 
recently Kühn found that in Andrecea the first is formed from the apical cell, the 
