486 
The Ohio Naturalist. 
[Vol. VI, No. 5, 
peculiar ring of cells by whose contraction the cavity of the 
sporangium is torn open on one side and the spores thrown out. 
When the spore germinates it gives rise to a short filament or 
protonema from the end of which a flat dorsiventral more or less 
heart-shaped thallus develops. The development of the gameto- 
phyte therefore falls normally into two distinct stages. In the 
first the plant body is a linear aggregate, in the second it is a 
solid aggregate. The thallus is supplied with abundant chloro- 
phyll and is attached to the earth by means of numerous uni- 
cellular rhizoids. The thallus is hermaphrodite and develops a 
number of antheridia or spermaries and archegonia or ovaries 
on the lower side. These organs are partly imbedded in the 
tissues of the thallus. A number of large spirally coiled, multi- 
ciliate spermatozoids are developed in each antheridium. These 
finally escape, when the thallus is covered with water, through a 
rupture in the outer part of the antheridial wall and after 
swimming around for a while enter the necks of the archegonia. 
The spermatozoids of the horsetails are also spirally coiled and 
multiciliate but those of the lycopods are small and biciliate. A 
single oosphere or egg is produced in each archegonium. The 
mother cell of the egg divides giving rise to the incipient egg and 
the ventral canal cell. The ventral canal cell and the cells in 
the neck of the archegonium dissolve and at the same time the 
cells at the end of the neck of the archegonium, the so called lid 
cells, separate leaving a passage from the outside down to the 
egg. A spermatozoid passes down the neck to the egg and con- 
iugates with it. This is fertilization, and during the union of the 
two cells their nuclei also unite, thus doubling the amount of 
chromatin in the cell. The fertilized egg or oospore, therefore, 
contains potentially 2x chromosomes which appear when ger- 
mination takes place. 
The egg germinates in the venter of the archegonium. First 
there is a diagonal or nearly vertical division into two cells and 
these each divide again, more or less at right angles to the first 
division, giving rise to the first four cells which are the incepts of 
the four regions present in the developing sporophyte embryo. 
One cell gives rise to the root tip, the second to the nourishing 
foot, the third to the stem tip, and the fourth to the first leaf. 
The developing embryo is entirely parasitic on the parent 
gametophyte which continues to manufacture food for a con- 
siderable length of time. Finally the embryo breaks through 
the wall of the enlarged venter of the archegonium and the root 
tip grows downward into the ground while the first leaf grows 
upward toward the light. Thus the ])teridophyte embryo 
always passes through a bryophyte stage. The embryo passes 
gradually from a parasitic life and becomes completely inde- 
