1gt0] PACE—FERN .PROTHALLIA 51 
instances this outgrowth is from the apical region, as shown in the 
diagram (fig. 3), which represents a small prothallium 5 mm. long. 
The outgrowth has antheridia along the margins, but shows no 
archegonia; these were present, however, on the main prothallium. 
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Fics. 3-6.—Fig. 3, prothallium 5 mm. long, with apical process bearing antheridia 
but no archegonia, which are found on the main prothallium; fig. 4, section throug 
a very young gametophytic branch with apical cell; the branch is at the edge of the 
section and near an archegonium, the cross-section of the neck of which is shown; 
fig. 5, section through the basal part of a gametophytic branch, showing its relation 
to the main gametophyte; fig. 6, an antheridial prothallium 23 mm. long, with many 
archegonia but eh esis oe F : ; 
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Sections of this prothallium show nothing unusual in structure or 
cell contents. 
A section of one of these branches at a very early stage shows its 
relation to the main prothallium (fig. 4). It comes from the edge 
of the archegonial cushion, the section showing also the neck of an 
adjacent archegonium. So far as the apical region is concerned, it 
