360 
MUSCINEM. 
segments; the lower parts together with the ventral segment are employed in the 
formation of the perigynium. The further development of the archegonia and antheridia 
has already been described. 
In the species examined by Hofmeister the fertilised oosphere is first divided by a 
transverse septum, i. e. at right angles to the axis of the archegonium. Only the upper 
of the two cells, the one towards the neck of the archegonium, becomes further divided, 
and it gives rise to four apical cells arranged as octants of a sphere, as described 
above. 
The basal portion of the growing archegonium becomes swollen out and penetrates 
down into the tissue of the stem, being nourished and firmly enclosed by it (the vaginula). 
As soon as the young sporogonium consists 
of a number of cells, its wall becomes differ- 
entiated from the inner tissue which is to 
form the spores and elaters. In Frullania it 
is a single circular disc of cells lying trans- 
versely beneath the dome of the young sporo- 
gonium from which the vertical elaters, and 
by further divisions, the mother-cells of the 
spores arise, a process which reminds one of 
what occurs in Sphagnum. In most true 
Jungermannieae there is, on the other hand, 
a column of tissue consisting of vertical rows 
of cells (surrounded by the wall of the sporo- 
gonium consisting of two layers), out of which 
the elaters and spores are formed. The elaters 
lie, in this case, horizontally, and radiate from 
the ideal longitudinal axis to the wall of the 
sporogoninm (Fig. 246). In Pellia the inner 
fertile tissue forms, after the differentiation of 
the wall of the sporogonium, a hemisphere, 
from the cells of which arise the spores and 
the elaters radiating from below upwards, in a 
similar manner to what occurs in the Mar- 
chantieae. 
By a rapid extension of the hitherto short seta, the calyptra is ruptured at the 
apex, and the globular sporogonium with the already ripe spores is raised up on it. 
Whilst the spores are ripening, the inner layer of the wall of the sporogonium becomes 
absorbed; the single layer which still remains is ruptured at the apex, and splits into four 
(rarely more) longitudinal valves, which, flying asunder in the form of a star, carry with 
them at the same time the elaters, by which the spores are dispersed. The elaters, when 
mature, are long fusiform thin-walled cells, round the interior of which run from one to 
three brown spiral bands. 
FIG. 246. — JtingermaJtnia bicuspidata ; longitudinal 
section of the unripe sporogonium sg, surrounded by tlie 
calyptra ar ; ar' archegonia which have remained unfer- 
tiHsed ; / base of the perigoniuni ; st stem ; b leaf ; points 
to the dilated base of the seta, which still bears the hypo- 
basal cell {after Hofmeister). 
