THE MORPHOLOGY AND SYSTEMATIC POSITION OF PODOMITRIUM 205 
nothing to indicate any deviation from what has been described for 
other related forms. The number of chromosomes in the sperm nucleus 
is eight, the same as has been found in Blyttia. 
The archegonia are in a group upon the dorsal surface of short 
lateral shoots (fig. i, C-E). These archegonial branches are so short 
that they are almost hidden by the large involucre which surrounds the 
archegonial group. No midrib is developed in the archegonial shoot 
which has the form of a thin nearly orbicular lamina with a more or 
less conspicuously toothed margin. The involucre has its margin 
composed of numerous slender appendages forming a dense fringe. 
The archegonia may number a dozen or more in a receptacle, and show 
different ages in the same group. They are borne upon a more or less 
evident elevation or placenta. Surrounding each group of archegonia 
is an inconspicuous elevated ridge or ring — the perianth. Should 
none of the archegonia be fertilized the perianth remains rudimentary ; 
but, where an embryo is developed, the perianth grows very rapidly 
and forms a tubular sheath which encloses the growing sporophyte 
and projects far beyond the involucre (fig. i, A, B). The margin of 
the perianth, like that of the involucre, is conspicuously fringed. 
Both involucre and perianth in Podomitrium are very much like 
those of Blyttia, and, except that the archegonia are produced on 
special branches, the two genera are scarcely distinguishable. The 
archegonia themselves (fig. 5) show no marked peculiarities, and are 
also practically identical in structure with those of Blyttia. There 
is usually a more or less evident stalk developed, and in the terminal 
cell of the young archegonium there are formed the usual three in- 
tersecting walls cutting out an axial cell from three peripheral cells. 
From the former the cap cell is now cut off, and this sooner or later 
divides by quadrant walls into the usual four terminal cells of the 
archegonium. This division generally takes place somewhat later in 
Podomitrium than is usual in the Liverworts, and sometimes it looks 
as if there was a limited apical growth of the young archegonium due 
to lateral segments cut off from the primary cap cell before its final 
division by quadrant walls (fig. D). In this respect Podomitrium 
Malaccense may be compared with Blyttia Levieri^, where a similar 
condition has been noted. It also recalls the apical growth in the 
moss archegonium, although, in the latter, canal cells are also cut off 
from the basal segments of the cap cell, while such limited apical growth 
^ Campbell and Williams, loc. cit. 
