McALLISTER: MORPHOLOGY OF THALLOCARPUS 121 
As the archegonia develop, plates of cells are formed about 
them in such a manner as to entirely submerge them at maturity. 
The antheridia arise back of the growing point of the male 
thallus in much the same position as the archegonium appears in 
the female plant. I have not followed the development of the 
antheridium in detail but there seems to be no noteworthy differ- 
ence between them and those of Riccia. From Fics. 6 and 7 it 
will be seen that the early stages of development conform entirely 
with those of Riccia, according to the accounts of Garber, Camp- 
bell, and Lewis. 
The fertilized egg divides by a wall transverse to the long 
axis of the archegonium (Fic. 8) as is the case with Riccia and 
the other Marchantiales. The subsequent divisions seem also 
to be the same as in Riccia, forming finally a sphere eight to ten 
cells across at the longest diameter. Divisions cease in the mass 
of sporophytic cells when the sporogonium is about half grown 
(Fic. 10). At this period the cells are all alike, no difference being 
observable between the cells that are later to form the wall and 
those that are to form the spore mother cells. 
Frequently, however, a number of sporophytic cells adjoining 
the neck canal, fix and stain differently from the rest of the cells 
of the sporophyte. They are usually smaller cells with denser 
protoplasmic content and with nuclei which are smaller and which 
take the stain more readily than those of the other cells of the 
sporophyte. From Fics. 9, 10, 11, and 12 it will be seen that they 
occur in sporophytes of all ages, except possibly those fully 
mature. Miss Black (5) has observed bacteria accumulated at the 
base of the neck canal in Riccia Frostit Aust., causing injury to the 
sporophytic cells of this region. It is possible that the above 
mentioned cells of the sporophyte of Thallocarpus may have been 
injured by secretions of bacterial origin though I have never ob- 
served bacteria-like structures in this region. 
The single layer of cells of the venter divides early to form 
two layers (Fic. 9). These cells enlarge with the division and 
enlargement of the cells of the sporophyte but do not themselves 
undergo further division. Their dimensions at the maturity a 
the sporophyte are at least three times as great as at first (FIGs. 
12,13). The outer layer of venter cells is seen early to be abund- 
