BRYOPHYTA 369 
The conspicuous stage in the life history is known as the 
gametophyte (Fig. 397), because it produces gametes. These are 
of two kinds, eggs and spermatozoids. The eggs are borne in 
flask-shaped odgonia, called archegonia (Fig. 398). An arche- 
gonium of a liverwort is a flask-shaped structure, the wall of 

Fig. 400. Antheridium (x 160) and 
a single spermatozoid of Riccia 
The antheridium consists of a stalk, 
a covering of sterile cells, and many 
sperm cells 
which is composed of a single 
layer of cells. The lower part 
of the archegonium is enlarged 
and contains a single large cell 
which, shortly before the arche- 
gonium matures, divides into 
two cells, the lower of which 
is a large egg, while the upper is smaller and is known as the 
ventral-canal cell (Fig. 398). The upper portion of the arche- 
gonium is elongated into a narrow structure called the neck. 
Within the neck is a row of neck-canal cells (Fig. 398). When 
the archegonium matures, the ventral-canal cell and neck-canal 
cells become disorganized and the top of the neck opens to dis- 
charge the remains of the canal cells (Fig. 399), after which the 
sperm can swim through the neck to the egg cell, The anther- 

Fic. 399. Mature archegonium of 
Riccia 
The neck-canal cells and ventral-canal 
cell have become disorganized. (x 240) 
