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Journal Article

Leaflets of Cycadaceae

M. Alice Lamb
Botanical Gazette
Vol. 76, No. 2 (Oct., 1923), pp. 185-202
Stable URL: http://www.jstor.org/stable/2469725
Page Count: 20
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Leaflets of Cycadaceae
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Abstract

1. A key based on topographical characters of leaflets is workable for genera. 2. The leaflets of the different species vary in color from bright green to dark green or dull gray-green; the shape and texture of the leaflets show an equal amount of variation. 3. A thick-walled, cutinized epidermis is characteristic of all the species examined; and a hypodermis is differentiated to some extent in all the species studied except Bowenia. 4. A well differentiated upper palisade is present in Cycas, Dioon, Encephalartos, Ceratozamia, Macrozamia, and Zamia furfuracea. Other species of Zamia show a more or less palisade region, but the cells are scarcely elongated or regular enough to constitute a true palisade. 5. The spongy mesophyll in most of the species examined is composed of transversely elongated cells. In nine of the species the cells are yoke-shaped. 6. In all of the species studied, thick-walled cells are found around the vascular bundles or scattered through the mesophyll. 7. Mucilage canals are present in Macrozamia, Dioon, Stangeria, and some species of Encephalartos. 8. In all of the species considered, except Bowenia serrulata, crystals of calcium oxalate are found. 9. Stomata were found on the upper as well as on the lower surfaces of the leaflets of Macrozamia Moorei and Bowenia serrulata. In the other species examined they were found on the lower surface only. 10. In studying the character of the leaflets two factors, heredity and environment, must be taken into consideration. The favorable environmental factors in greenhouse cultivation have perhaps modified the xerophytic structure of the leaflets studied.

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