Your PDF has successfully downloaded.

You may be interested in finding more content on these topics:

Access

You are not currently logged in.

Access JSTOR through your library or other institution:

login

Log in through your institution.

Journal Article

Microcycas Calocoma

Otis W. Caldwell
Botanical Gazette
Vol. 44, No. 2 (Aug., 1907), pp. 118-141
Stable URL: http://www.jstor.org/stable/2465772
Page Count: 28

You can always find the topics here!

Topics: Plants, Gametophytes, Mother cells, Plant cells, Spermatozoa, Cell nucleus, Pollen tubes, Embryos, Ovules, Branches
Were these topics helpful?
See somethings inaccurate? Let us know!

Select the topics that are inaccurate.

Cancel
  • Download PDF
  • Add to My Lists
  • Cite this Item
We're having trouble loading this content. Download PDF instead.

Abstract

1. Small and widely separated groups of Microcycas calocoma occur in some of the mountains of western Cuba. 2. The adult plant is a small tree, and reaches the greatest height and circumference yet recorded for any cycad indigenous to the western hemisphere. The stem may be a straight shaft or may branch many times. 3. The ovulate cone is the largest known; and it and its sporophylls bear more resemblance to those of Zamia than to those of other cycads. 4. Unbranched vascular bundles pass up the stalk of the megasporophyll, anastomose in the expanded portion, then give off five to eight branches to each ovule. Immediately after entering the ovule each branch divides, one subdivision passing unbranched through the fleshy layer, and the other passing into the hard layer and branching many times. 5. The staminate cone is long and slender, and two-thirds of the abaxial side of its sporophylls is densely covered by sporangia which do not show any distinct grouping into sori. 6. In the male gametophyte eight body cells are formed and sixteen sperms. Each body cell has two large blepharoplasts which usually lie on opposite sides of the cell, but sometimes may lie side by side. Sometimes nine or ten body cells are produced. 7. The female gametophyte is often prominently lobed, and develops a large number of archegonia (sometimes exceeding 200), which are produced on any part of the surface or even within the endosperm. 8. Many embryos are produced, the suspensor being very long and spirally coiled and pressing the embryo tip against the endosperm; the cotyledons are three to six in number. 9. Microcycas may be regarded as the most primitive cycad yet described.

Notes and References

This item contains 16 references.

Literature Cited
  • 1
    CALDWELL, O.W., and BAKER, C. F., The identity of Microcycas calocoma. BOT. GAZ. 43:330-335. figs. 3. 1907.
  • 2
    MIQUEL, A. F. XV., Sur une espece nouvelle de Zamia des Indes occiden- tales, introduite dans l'etablissement Van Houtte, 'a Gand. Van Houtte's Fl. Serres et Jard. 7:141. 1851.
  • 3
    DECANDOLLE, A., Microcycas calocoma. DC. Prodr. 162:538. 1868.
  • 4
    CHAMBERLAIN, C. J., The ovule and female gametophyte of Dioon. BOT. GAZ. 42:321-358. pIs. I3-I5. figs. I-9. 1906.
  • 5
    STOPES, M. C., On the double nature of the cycadean integument. Annals of Botany 19:561-566. 1905.
  • 6
    WEBBER, H. J., Spermatogenesis and fecundation of Zamia. Bull. 2, U. S. Bureau of Plant Industry. pp. 100. pis. 6. 1901.
  • 7
    IKENO, S., Untersuchungen fiber die Entwickelung der Geschlechtsorgane und der Vorgang der Befruchtung bei Cycas revoluta. Jahrb. Wiss. Bot. 32:557-602. pis. 8-iO. 1898.
  • 8
    HIRASÉ, S., Etudes sur la f6condation et l'embryogenie du Ginkgo biloba. Jour. Imp. Coll. Sci. Tokyo 8:307-322. pIs. 3I-32. 1895.
  • 9
    LANG, W. H., Studies in the development and morphology of cycadean sporangia. II. The ovule of Stangeria paradoxa. Annals of Botany 14: 281-306. pis. I7-I8. 1900.
  • 10
    COULTER, J. M., and CHAMBERLAIN, C. J., The embryogeny of Zamia. BOT. GAZ. 35: 184-I94. pis. 6-8. 1903.
  • 11
    COKER, W. C., On the gametophytes and embryo of Taxodium. BOT. GAZ. 36: 1-27, II4-I40. pis. I-II. 1903.
  • 12
    . , Notes on the gametophytes and embryo of Podocarpus. BOT. GAZ. 33:89-I07. pis. 5-7. 1902.
  • 13
    GOROSCHANKIN, J., Zur Kenntnis der Corpuscula bei den Gymnospermen. Bot. Zeit. 41:825-83I. Pl. 70. 1883.
  • 14
    TREUB, M., Recherches sur les Cycadees. 3. Embryogenie du Cycas cir- cinalis. Ann. Jard. Bot. Buitenzorg 4:1-II. pis. I-3. 1884.
  • 15
    SMITH, M. ISABEL, The nutrition of the egg in Zamia. BOT. GAZ. 37: 346-352. figs. 6. 1903.
  • 16
    STOPES, M. C., and Fujii, K., The nutritive relation of the surrounding tissues of the archegonia in gymnosperms. Beih. Bot. Centralbl. 20: 1-24. pl. I. 1906.