228 
P. Cavers. 
scales, or a single scale, or the inturned and fringed edges of the 
female branch, suffices for the protection of the archegonia (by 
forming capillary water-holding spaces), the developing sporogonium 
requires a more complete cylindrical investment which may be 
provided in the form of a massive calyptra or of a special tubular 
outgrowth of the surrounding tissue. 
The thick calyptra on the one hand, and the tubular perianth on 
the other, have apparently arisen independently in several lines of 
development; we meet with both in genera belonging to the other 
groups—the perianth in Calycularia, Noteroclada, Fossombronia, 
and Petalophyllum , and the massive calyptra in Treubia and the 
Calobryaceae. In all the foliose Codoniaceae (except Bias id), as in 
the Calobryaceae, the archegonia are protected by the leaves ; in 
Blasia and in Pellia they are sunk in a cavity in the axis of the 
plant-body, and in Calycularia there is a cupule-like involucre formed 
from scales. In all the Codoniaceae, except Blasia, the capsule is 
spherical, and its wall is provided with fibrous thickenings. In 
Fossombronia and Petalophyllum, the capsule-wall breaks up into 
plates, and there is no trace of an elaterophore, but in the other 
genera, dehiscence occurs by four valves and there is always a more 
or less highly developed basal elaterophore. The latter reaches its 
greatest development in Pellia and Noteroclada, but in most of the 
other genera is represented only by isolated fixed elater-like cells 
at the base of the capsule-cavity. 
The Codoniaceae are sharply marked off from the Blyttiaceae 
and Aneuraceae by the capsule structure, especially by the basal 
elaterophore. The two latter families should perhaps be merged 
into one. Podomitrium connects the Aneuraceae with the Blyttiaceae, 
having the following characters in common with the genus Blyttia : 
perianth laid down before fertilisation occurs in the archegonial 
group, and formed by outgrowth of several fringed scales which are 
carried up to form a tube by basal growth; cells of capsule-wall 
uniformly thickened, without fibres; elaterophore represented only 
by an apical pad of thin-walled cells ; capsule-wall and elaterophore 
do not split at the top. In Umbraculum, which is frequently joined 
to Podomitrium to form the genus Hymenophytum, the perianth is 
laid down before fertilisation, and arises not from scales but from a 
ring-like outgrowth; the outer cells of the capsule-wall have fibrous 
thickenings; the capsule opens by four free valves, the elaterophore 
splitting into four parts which adhere to the tips of the valves, as 
in Aneura and Metzgeria. Makinoa, though probably more closely 
