38 



Our Native Ferns. 



Fig. 25. Antheridium of 

 Adiantum Capillus-Veneris, 

 L., showing the escaping 

 antherozoids. {After Sachs.) 



water and finally bursts its wall, dis- 

 charging these coiled filaments which 

 possess the power of locomotion, and 

 for this reason are called antherozoids. 

 These antherozoids often drag with 

 them a little vesicle which seems to 

 play no part in the process of repro- 

 duction. (Fig. 25). 



70. Archegonia. — The archego- 

 nium (sometimes called pistillidium), 

 is also a rounded mass of tissue usu- 

 ally less prominent than the anthe- 

 ridia, consisting of an external layer 

 of cells and a large central cell which 

 soon divides into two. The lower por- 

 tion, at first the larger, develops into 

 a roundish cell, which is analogous to 

 the ovule of flowering plants and is 

 called the oosphere . The upper por- 

 tion of the central cell develops be- 

 tween those composing the neck of 

 the archegonium into a canal filled 

 with a sort of mucilage ; this finally 

 swells up, forces the cells of the 

 neck apart, and is expelled to aid in 

 attracting and retaining the anthe- 

 Mg. 26. Yonni^ archegonium wzoids at the neck of the arche- 

 of Pterissem(!a(a, Linn, f., show- gonium. The oosphere is thus left ex- 



ingoosphere, neck and canal-cell poSed. (Fig. 26). 

 (After Sachs.) 



71. Fertilization. — The antherozoids, analogous to the pollen 

 of flowers, when discharged from the antheridium, swim in the 

 moisture always present on the under surface of the prothallium, 

 swarm in large numbers around the neck of the archegonium 

 and are retained by the mucilage. Some finally force their way 

 into the canal of the neck, a few reaching the oosphere and dis- 

 appearing within its substance. There is thus a true sexual gene- 

 ration among ferns, and the formerly appropriate term, Crypto- 

 gaviia (hidden marriage) loses its application under the untiring 

 scrutiny of the microscopist. After fertilization the neck of the 

 archegonium closes and the fertilized oosphere, now called the 

 oospore, increases in size and finally develops into a true fern. 



