1904) ‘DAVIS—SEXUAL ORGANS IN PLANTS 247 
The origin of the sexual organs of the bryophytes and pterido- 
phytes is necessarily a matter of speculation, but the relation that 
they bear to one another and the type of structure which they repre- 
sent are much more clearly understood than formerly. These game- 
tangia are essentially cellular capsules composed of an outer layer 
of sterile cells which encloses a central mass of gametogenous tissue. 
The development of the antheridium and archegonium generally 
starts from a superficial cell, which by various divisions differentiates 
a single terminal cell or a group of terminal cells that become the 
growing points of the structure, building it up from above. Thus the 
antheridium and archegonium are from the beginning and at all 
times tissues of a definite form whose cooperating cells establish the 
organ. They are not structures of the same class as certain assem- 
blages of independent gametocysts whose cells are massed into definite 
form, as for example many so-called antheridia of the red algae. 
It seems to be perfectly clear now that the central region of cells 
within the capsule wall of both antheridium and archegonium are 
phylogenetically gametogenous tissues and are homologous; or, 
expressed concretely, that the canal cells of the archegonium are 
reduced and degenerate gamete mother-cells which together with the 
fertile egg cell are homologous with the sperm mother-cells. This 
view, which has been held tentatively by many botanists for a long 
ime, is supported especially by observations by Hy and TREUB, 
and the recent studies of Hoxrerty and Lyon. GoesEL (’o2) in 
“n important paper has discussed the homologies of the sexual organs 
" bryophytes and pteridophytes, recognizing that the suppression of 
i division and a process of sterilization were largely responsible for 
the peculiarities of the female. He also clearly showed the difficulties 
= throw so much doubt on G6rz’s theory of a relationship between 
© archegonium and oogonium of the Charales. 
Fiat: i P- 121) noted that various species of mosses present occa- 
= y the transformation of archegonia into antheridia, a phenome- 
" apparently frequent in Atrichum undulatum. Treus’s (’86, 
PP. *07~108) observations on Lycopodium Phlegmaria are of the 
3 — oo He found that the canal cells may eee THF 
ee ‘t - he figures an archegonium in which a canal cell is divide 
studinally so that the axial row is double at that point. A dia- 
