. Foundations of Botany. Botany. TYPES OF CRYPTOGAMS; PTERIDOPHYTES 289 cover with a large cover-glass, and examine with the lowest power of the microscope. Xote : (a) The abundant root-hairs, springing from the lower surface of the prothallium. (b) The variable thickness of the prothallium, near the edge, consisting of only one layer of cells. (c) (In some mature specimens) the young fern growing from the prothallium, as shown in Fig. 211, B. The student can hardly make out for himself, without much expenditure of time, the structure of the antheridia and the arche- gonia (Fig. 211, .4), by t
. Foundations of Botany. Botany. TYPES OF CRYPTOGAMS; PTERIDOPHYTES 289 cover with a large cover-glass, and examine with the lowest power of the microscope. Xote : (a) The abundant root-hairs, springing from the lower surface of the prothallium. (b) The variable thickness of the prothallium, near the edge, consisting of only one layer of cells. (c) (In some mature specimens) the young fern growing from the prothallium, as shown in Fig. 211, B. The student can hardly make out for himself, without much expenditure of time, the structure of the antheridia and the arche- gonia (Fig. 211, .4), by the cooperation of which fertilization takes place on much the same plan as that already described in the case of mosses. The fertilized egg- cell of the archego- nium gives rise to the young fern, the sp o rop hyte which grows at first at the expense of the parent prothallium but soon develops roots of its own and leads an in- dependent existence. 353. Nutrition.— The mature fern makes its living, as flowering plants do, by absorption of nutritive matter from the soil and from the air, and its abundant chlorophyll makes it easy for the plant to decompose the supplies of carbon dioxide which it takes in through its Fig. 211. — Two Prothallia of a Fern (Aspidium). A, under surface of a young prothallium ; ar, arche- gonia ; an, antheridia ; r, rhizoids ; B, an older pro- thallium with a young fern-plant growing from it; I, leaf of young fern. (Both x about 8.). 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 Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn & company
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1901
