. Our native ferns and how to study them; with synoptical descriptions of the North American species. Ferns. Fructification. 29 lines, or may even be spread in a stratum over tiie entire under surface of the frond. They may be indusiate or non-indusiate according as they are covered or naked; and the indusia may be inferior (attached below the sorus), as in Woodsia (Fig. 12), or su- perior as in Aspidium (Fig. 11), or of various intermediate meth- ods of attachment. , Fia. 4. Fio. 6. Fig. 3.—Enlarged sessile sporangium of TrichomjaTies radicana, Swz. (Original.) Fig. 4.—Sporangium of Sch
. Our native ferns and how to study them; with synoptical descriptions of the North American species. Ferns. Fructification. 29 lines, or may even be spread in a stratum over tiie entire under surface of the frond. They may be indusiate or non-indusiate according as they are covered or naked; and the indusia may be inferior (attached below the sorus), as in Woodsia (Fig. 12), or su- perior as in Aspidium (Fig. 11), or of various intermediate meth- ods of attachment. , Fia. 4. Fio. 6. Fig. 3.—Enlarged sessile sporangium of TrichomjaTies radicana, Swz. (Original.) Fig. 4.—Sporangium of Schiz3ea p^^tUa, Pursh, showing the apicil ring. Much en- larged. (Original.) Fig. 5.—Sporangium of Osmunda regalis, L., showing the rudimentary ring. Enlarged. (Original.) 32. In the other sub-orders of Filices the sporangia are va- riously arranged. In the Hymenophyllace^ or filmy ferns the flattened sporangia are sessile along a filiform receptacle and are surrounded with a complete transverse ring. At maturity they open vertically, (Fig. 3). In the ^ the sporangia are ovatei surroundedat the apex by a complete ring, and open by a longitud- inal slit. (Fig. 4). In the Osmundace^ or flowering ferns the sporangia are larger, globose and naked, with the mere trace of a transverse ring, and open longitudinally. (Fig. 5). 33. In Order Ophioglossace^ the spor- angia are not reticulated, possess no trace of a ring, open by a transverse slit, and are various- ly spiked and panicled. (Fig. 6). The various methods of fructification can be best understood by describing the peculiar- ities of the various genera in regular succes- sion and noting the variations occurring in the sections or sub-genera. By this means we will arrive at a belter understanding of the princi- ples of fern classification as discussed in a future chapter. As the subject of venation is closely connected with that of fructification, it will be treated in the same Fig. G.' Enlarged spo. ra
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