. A manual of botany. Botany. 380 MA>:UAL OF BOTANY In Monocotyledons and Vascular Cryptogams no cambium layer is developed in the roots, which consequently increase in thickness only very slightly. Coincidently with the development of the secondary vascular tissue in the stele, a phellogenlayer arises, usually in the pericycle, though sometimes in the cortex, which forms cork externally Fie. Fig. 767. Section of root showing secondary thiclcening. eii. Endodermis. Primary xylem bundles. }t. Primary pliloem bundle, Masses of secondary xylem formed opposite to the
. A manual of botany. Botany. 380 MA>:UAL OF BOTANY In Monocotyledons and Vascular Cryptogams no cambium layer is developed in the roots, which consequently increase in thickness only very slightly. Coincidently with the development of the secondary vascular tissue in the stele, a phellogenlayer arises, usually in the pericycle, though sometimes in the cortex, which forms cork externally Fie. Fig. 767. Section of root showing secondary thiclcening. eii. Endodermis. Primary xylem bundles. }t. Primary pliloem bundle, Masses of secondary xylem formed opposite to the latter, c. Cambium. Opposite to the primary xylem the cambium has only formed parenchyma, consti- tuting large secondary medullary rays. After Kny. and phelloderm on its inner face, as in the stem. The tissues external to this periderm formation dry up and are thrown off, so that the exterior of the root is covered by a layer of cork, usually of stelar origin. The phellogen continues active for some time, and then becomes either cork or permanent paren- chyma. A new phellogen subsequently arises in the new-formed. 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 Green, J. Reynolds (Joseph Reynolds), 1848-1914. London, J. & A. Churchill
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