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 normalh' 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- 

 jugates 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 pterido})hyte embryo 

 always passes through a bryophyte stage. The embryo passes 

 gradually from a parasitic life and becomes completely inde- 



