The Sporing of the Fern 255 
ion of the prothallus, the archegonia, which are the 
reasons of their being. An archegonium also be- 
gins life as a single cell, on the under surface of 
the prothallus. A little later a crosswise parti- 
tion appears, dividing the cell into an upper and 
a lower portion. More par- 
titions are formed, making a 
cluster of cells, while the life 
of the prothallus mould the 
plastic young tissue till the 
maturing archegonium takes 
the shape of a flask, with a 
proportionately very long and 
thick neck, curved over to 
one side (Fig. 70). 
The curve is generally in 
such a direction that the 
mouth of the flask points 
toward an antheridium. 
F Fic. 7o.—Young archego- 
At first the flask’s mouth nium of a garden maidens 
: é , hair (Adiantum cuneatum). 
is closed, and its neck is (Much magnified.) 
filled with a row of cells, called the ‘‘neck-canal 
cells.” But a little later these dissolve into muci- 
lage, and at the same time the lips of the flask 
draw apart. And from the flask’s mouth, at this 
date in its history, there is discharged an acid 
