1915] HUTCHINSON—PELLIA EPIPHYLLA 141 
archegonial form (G, H, J) the first wall (1) is not median, but some- 
what laterally placed and inclined; there is no wall no. 3; the 
section corresponding to the quadrants C and D does not divide, 
but remains as a sterile wall cell. Wall 2 again cuts off a section 
corresponding to quadrant A, which also persists as a sterile wall 
cell. A periclinal wall (5) divides the section corresponding to 
quadrant B into a wall cell and a spermatogenous cell. Three 
of the quadrants have become sterile. Starting with the Mar- 
chantiales form of antheridia, by the sterilization of alternate 
quadrants the Jungermanniales form is derived; and by the 
sterilization of three quadrants the archegonial form results. The 
sterilization sequence corresponds to the time sequence as de- 
scribed above. 
Only one step is lacking in this series to complete the transition 
from the antheridium of Marchantiales to the archegonium, namely 
the reduction of the spermatogenous mass into a single row of cells, 
only one of which, the egg, shall be functional. Such transition 
forms have been described by Davis® in Marchantiales. The 
writer has seen such “‘archegonia”’ with gamete masses in sections 
prepared by Dr. W. J. G. Lanp. The antheridial forms of P. epi- 
phylla furnish evidence that the various types of antheridia and the 
archegonium have had a common origin, possibly gametangia resem- 
bling in structure the antheridium of Marchantiales. 
Relationships 
The genetic relationships of P. epiphylla, because of its diversity, 
present a rather complex problem. With respect to its relation 
to other species of the genus Pellia, if the other species retain 
throughout life the form of apical cell ascribed to them, it would 
follow that P. epiphylla has branched sooner from the general 
line of progress and has retained and developed generalized char- 
acters. As a member of the Jungermanniales, this species is 
acrogynous in the sense that growth is checked, apical growth is 
stopped, by the production of archegonia. It differs from the more 
characteristic Acrogynae in having several regions of growth, each 
of which is checked in the same way. It is possible that acrogyny 
° Davis, B. M., The origin of the archegonium. Ann. Botany 17: 477-492. 1903. 
