File:Foundations of botany (1901) (14784201035).jpg

Identifier: foundationsofbot00berg (find matches)
Title: Foundations of botany
Year: 1901 (1900s)
Authors: Bergen, Joseph Y. (Joseph Young), 1851-1917 Bergen, Joseph Y. (Joseph Young), 1851-1917. Bergen's Botany: key and flora, Northern and Central States ed. 1901
Subjects: Plants
Publisher: Boston : Ginn
Contributing Library: The LuEsther T Mertz Library, the New York Botanical Garden
Digitizing Sponsor: The LuEsther T Mertz Library, the New York Botanical Garden

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ut all these points. Examine some of the sporangia, dry, with a power of about fiftyor seventy-five diameters, and sketch. Scrape off a few sporangia,thus disengaging some spores, mount the latter in water, examinewith a power of about 200 diameters, and draw. 352. Life History of the Fern. — When a fern-spore is sown ondamp earth it gradually develops into a minute, flattish object,called a prothallium (Fig. 211). It is a rather tedious process togrow prothallia from spores, and the easiest way to get them forstudy is to look for them on the earth or on the damp outer surfaceof the flower-pots in which ferns are growing in a greenhouse. Allstages of germination may readily be found in such localities. Any prothallia thus obtained for study may be freed from par-ticles of earth by being washed, while held in very small forceps, ina gentle stream of water from a wash-bottle. The student shouldthen mount the prothallium, bottom up, in water in a shallow cell, 288 FOUNDATIONS OF BOTANY
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Fig. 210. — Spore-Plant of a Fern (Aspidium Filix-mas).A, part of rootstoek and fronds, not quite one-sixth natural size ; fr, young frondsunrolling ; B, under side of a pinnule, showing sori, s ; C, section through asorus at right angles to surface of leaf, showing indusium, i, and sporangia, s ;D, a sporangium discharging spores. (B is not far from natural size. C andD are considerahly magnified.) TYPES or CRYPTOGAMS; PTERIDOPHYTES* 289 cover with a large cover-glass, and examine with the lowest powerof the microscope. Note : (a) The abundant root-hairs, springing from the lower surfaceof 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 fromthe prothallium, as shown in Fig. 211, B. The student can hardly make out for himself, without muchexpenditure of time, the structme of the antheridia and the arche-gonia (Fig. 211, A),by the cooperationof which fertilizatio

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