. Heredity and evolution in plants . FIG. 4.—Tree ferns on the military road between Cayey and Caguas,Porto Rico. (Photo by M. A. Howe.) history of the individual. The various stages of lifehistory common to most plants are nowhere more clearlyillustrated than in the ferns. 2. Description of a Fern Plant.—The more commonferns of temperate regions have underground stems orrhizomes (sometimes called root-stocks), so that only the 4 MKRK1MTY AND KV< IN PLANTS leaves appear above The stem may be branchedor unbranched. When branched, the branches are pro-duced without reference
. Heredity and evolution in plants . FIG. 4.—Tree ferns on the military road between Cayey and Caguas,Porto Rico. (Photo by M. A. Howe.) history of the individual. The various stages of lifehistory common to most plants are nowhere more clearlyillustrated than in the ferns. 2. Description of a Fern Plant.—The more commonferns of temperate regions have underground stems orrhizomes (sometimes called root-stocks), so that only the 4 MKRK1MTY AND KV< IN PLANTS leaves appear above The stem may be branchedor unbranched. When branched, the branches are pro-duced without reference to the insertion of the leaves,in contrast to the habit of higher plants of formingbranches only in the upper angle (axil) between the stemand leaf-stalk. There is always a terminal bud at the. FIG. 5.—A, Upper epidermis; B, lower epidermis of the leaf of the fern,Drynaria mcyen-iana. (Camera lucida drawing.) tip of the fern-stem (and of the branches when any oc-cur) ; and the leaves arc usually attached just back of thistip. The stems are commonly (though not always)covered by hairs or scales (Fig. i), and on their olderportions, at some distance back from the tip, may be seenthe scars, or the ends of leaf-stalks, left by old leaves that 1 The leaves of ferns are often called fronds. LIFE HISTORY OF A FERN have died and fallen away. The rhizome bears true roots(Fig. 2), and its tissues are differentiated into epider-mal, fundamental, mechanical, and conducting systems(Fig. 3). In tropical countries there are tree ferns,
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Keywords: ., bookcentury1900, bookdecade1920, bookidheredityevol, bookyear1920
