. Heredity and evolution in plants . 3.—Cross-section of the rhizome of the bracken fern (Plcris aqul-liiui), showing the tissue systems. Greatly magnified. LIFE HISTORY OI- A 1KRN 3 embryo, and the embryo matures into an adult. By aseries of more or less complicated processes the adulteventually gives rise to another egg, like the one fromwhich it came, thus completing one life-cycle and initiat-ing another. These various changes constitute the life. 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
. Heredity and evolution in plants . 3.—Cross-section of the rhizome of the bracken fern (Plcris aqul-liiui), showing the tissue systems. Greatly magnified. LIFE HISTORY OI- A 1KRN 3 embryo, and the embryo matures into an adult. By aseries of more or less complicated processes the adulteventually gives rise to another egg, like the one fromwhich it came, thus completing one life-cycle and initiat-ing another. These various changes constitute the life. 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
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Keywords: ., bookcentury1900, bookdecade1920, bookidheredityevol, bookyear1920
