. Heredity and evolution in plants. Heredity; Plants. LIFE HISTORY OF A FERN 29 being entirely so; while in other cases sporangia occur on the foliage-leaf. As in the re- placement of sporophylls by sterile leaves in the ostrich fern, Onoclea struthiopteris (para- graph 8), these abnormalities indicate the close relationship between leaves and spore-bear- ing organs, and clearly show that the latter may be com- pletely transformed, by sterili- zation, into foliage-leaves. In Ophioglossum the foliage- leaf and spore-bearing spike are both unbranched, the latter suggesting an adder's tongue, whe
. Heredity and evolution in plants. Heredity; Plants. LIFE HISTORY OF A FERN 29 being entirely so; while in other cases sporangia occur on the foliage-leaf. As in the re- placement of sporophylls by sterile leaves in the ostrich fern, Onoclea struthiopteris (para- graph 8), these abnormalities indicate the close relationship between leaves and spore-bear- ing organs, and clearly show that the latter may be com- pletely transformed, by sterili- zation, into foliage-leaves. In Ophioglossum the foliage- leaf and spore-bearing spike are both unbranched, the latter suggesting an adder's tongue, whence the name, Ophioglossum. In both Ophioglossum and Botry- chium the sporangia originate from a group of epidermal and sub-epidermal cells, and are consequently imbedded in the surrounding tissue. Their walls are more than one cell in thick- ness, the annulus is lacking, and they open by a slit. Ferns of this type culled eusporangiate {Cf. p. I o). Their pro thallia are usually fleshy and subterranean, bear the antheridia and arche- gonia on the dorsal instead of on the ventral surface, and are per-. FiG. 28.—Adder's tongue fern {Ophioglossum vvlgatum L.). B, runner or Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gager, C. Stuart (Charles Stuart), 1872-1943. Philadelphia, P. Blakiston's Son & Co.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectplants, bookyear1920
