Davis . — The Origin of the Archegonium. 481 
the selected egg lies at the bottom of the capsule in the 
position most favourable for its own nourishment and for 
the protection and assistance offered to the young sporo- 
phyte. 
The primitive archegonium and antheridium, then, agree in 
all essentials of structure, and are homologous. They are both 
multicellular from the beginning, the form is generally de- 
termined by a growing point, and the final result is a sterile 
capsule enclosing a mass of gamete mother-cells, very nu- 
merous in the antheridium, but so reduced in the archegonium 
that only one gamete matures. 
It is not necessary in this discussion to consider the changes 
that come over the archegonium and antheridium in the higher 
groups of the Pteridophytes and in the Spermatophytes. The 
general trend is always towards the simplification and reduc- 
tion of cell structure until many features of the primitive 
organs are lost. We are not concerned with these later con- 
ditions, but only with the older, more generalized form of 
organ, best illustrated to-day among the Liverworts and 
Mosses. 
A comparison of the archegonium with the sexual organs 
of heterogamous Algae brings out great and fundamental 
differences. Chara and Coleochaete are the forms naturally 
considered in this connexion, because their sexual organs 
become invested with a cellular envelope, so that the eggs 
either before or after fertilization lie in a capsule. But the 
development of these organs shows clearly that the final struc- 
ture is not a unit, but a composite of several independent 
elements. The eggs are produced in oocysts after the method 
usual to Algae. The enveloping capsules are formed of inde- 
pendent filaments which, arising from cells below the oocysts, 
have absolutely no organic relation to the latter. 
The conditions in the Charales are further complicated by 
the peculiar small cells (Wendungszellen) that are cut off from 
the egg-cell before its maturity. The significance of these 
accessory cells has long been a matter of conjecture. There 
appears to be no reduction of the chromosomes with their 
