lOO 
F. Cavers. 
of three or four, each group sunk in a cup-like depression 
Fig. 9. Corsinia marchantioides. A, longitudinal section of thallus with 
three sporogonia. B, a part of A enlarged ; in., involucre ; cal M calyptra ; 
mingled with the developing spores are the starch bearing sterile cells. 
Immediately behind the group there arises a hood-like outgrowth 
which bends forward over the archegonia (Fig. 10); this involucre is 
several cells thick but contains no chambers, and it is formed quite 
independently of fertilisation. The cells forming the capsule-wall 
are strengthened by U-shaped fibres deposited on the inner and 
radial walls ; the sterile archesporial cells persist after the ripening 
of the spores and bear annular or spiral fibres, hence they are 
definite though short elaters. 
