209 
A nacrogynous Jungermanniales. 
and covered from behind by a hood-like scale. The archegonial 
groups, also borne dorsally, are each surrounded by a short cupule- 
like involucre formed from a series of toothed scales and by a much 
longer perianth which is laid down before fertilisation occurs, 
exactly as in Podomitnum ; within the perianth is the calyptra, 
which is about the same length or a little longer and which usually 
bears near the top the unfertilised archegonia. The capsule has 
much the same structure as in Podomitnum, and it usually opens 
by two to four slits, the valves generally remaining attached at the 
top, where there is a cap-like mass of tissue. 
Fig. 35. Morckia flotowiana. Part of a longitudinal section of the midrib, 
traversing one of the conducting strands. On either side of the elongated 
hyaline strand-cells are the cortical cells, packed with starch grains. X 180. 
In Morckia, the thallus is always creeping, as in the “ Repentes” 
section of Blyttia, with a broader midrib and less sharply defined 
wings, the latter being frequently wavy, (Fig. 32) but never showing 
incipient differentiation of leaves. In M. Flotowiana the midrib 
contains two strands of elongated cells (Figs. 33-35), but these are 
of much simpler structure than the strands of Blyttia, Symphyogyna, 
Podomitrium, and Umbraculum. There are small filamentous 
appendages on the lower side of the thallus, especially at the 
growing point (Fig. 36), and in M. Blyttii numerous small leaf-like 
appendages are borne on the upper surface along the midrib. These 
appendages are similar to the scales which in all species of Blyttia 
and Morckia cover the antheridia. In Morckia the antheridia are 
sometimes developed in more than two rows, and the scales covering 
them are more or less fused together, so that the antheridia appear 
to be sunk in chambers (Fig. 36) in the upper tissue of the thallus. 
The involucre and perianth in Morckia resemble the corresponding 
structures in Blyttia, but the capsule-wall has from three to five 
layers of small cells within the outer layer of large cells (Fig. 37). 
