Torr] FERGUSON—IMBEDDED SEXUAL CELLS 445 
cided as to whether it should be an antheridium or an archegonium; 
but the arching in such cases is insufficient to make the resulting 
organ completely superficial. 
The first wall laid down in the development of the imbedded 
antheridium is in the same plane as under normal conditions, 
but it may be deep-seated and little or not at all saucer-shaped 
(figs. 2, 3, 5). The second wall cuts out a central cell which may 
be very dome-shaped or may not be arched at all (figs. 2, 3, 5, 7, 8). 
The third wall follows in normal succession, cutting out the cover 
cell (figs. 5, 7, 8). The divisions occurring in the central cell of 
these antheridia in Pteris are somewhat different from those occur- 
ting in Dryopteris and Nephrodium as described by Miss BLAck. 
The first wall may sometimes be anticlinal and divide the cell into 
two equal cells, as is true under normal conditions (fig. ga); but 
in the majority of cases observed the central cell of the entirely 
sunken antheridium was divided by two slightly oblique anticlinal 
walls into three cells lying in the same plane (figs. 7, 8). 
Later stages in the development of the antheridium could not 
be traced beyond a question in the material at hand. But sooner 
or later a mass of cells occurs, from which the sperms are eventually 
Produced. In order to meet the needs of the enlarged antheridium 
the one cover cell is replaced by a cell complex. As a rule, the 
mature imbedded antheridium is covered by a single layer of cells, 
ut it may become two cells deep (fig. 10). In all cases observed, 
the imbedded antheridium is surrounded by a layer of cells much 
smaller than those which form the venter of an archegonium in 
the ferns, suggesting very strongly in their arrangement and appear- 
ance tapetal cells (figs. 10-12). 
The size of the young, partially imbedded antheridia is prac- 
Ucally the same as that of the normal antheridia, as is seen by a 
Comparison of figs. 1 and 3, and figs. 5 and 6. But in later stages 
of development these unusual antheridia may become greatly 
enlarged. The more deeply sunken the antheridium the greater 
the size is apt to be at maturity. A normal, mature antheridium 
's shown in fig. 13. Compare this both as to position and size 
with the antheridia illustrated in figs. 11 and 12. Fig. 12 does 
hot represent the largest antheridium observed. It was figured 
