. Our native ferns and their allies : with synoptical descriptions of the American Pteridophyta north of Mexico. Ferns. At maturity the antheridium swells by the absorption of 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. 24). 73. Archegonia. — The archego- nium (sometimes called pistillidium), is also a rounded mass of tissue usu- ally less prominent than the an
. Our native ferns and their allies : with synoptical descriptions of the American Pteridophyta north of Mexico. Ferns. At maturity the antheridium swells by the absorption of 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. 24). 73. 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- rozoids at the neck of the arche- gonium. The oosphere is thus left exposed. (Fig. 25). Fig. 24. Antheridium of Admnium Capillus - Veneris, L., showing the escaping antherozoids. (After Sachs.). Fig. 25. Young archegonium of Pteris serrulata, Linn, f., show- ing oosphere, neck and canal-cell. (After Sachs.) 74. 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- gamia (hidden marriage) loses its application under th
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