Ovulate Strobili Research Articles

Morphology of Ceratozamia

1. Ceratozamia mexicana grows best in well shaded mesophytic conditions. 2. Any individual in passing from the seedling to the adult stage shows such a progressive change in its leaves, the leaflets becoming larger, broader, thicker, and more numerous, that descriptions of species based largely upon leaves are open to suspicion. 3. The ovulate strobilus shows considerable variation in the size and number of its sporophylls. 4. In addition to the primary haustorium, a system of secondary haustoria is developed later from the basal portions of the pollen tube. There are regularly two sperms, but occasionally four are produced. 5. A small ventral canal nucleus is present, but occasionally it enlarges and may fertilize the egg. It is suggested that this may explain the so-called hybrids obtained by Van Tieghem. In most cases fertilization occurs in the usual way. 6. Both suspensors and young embryos may unite, so that from five fertilized eggs there may come one to five embryos. In the mature seed, as found in nature, there is one embryo with a single cotyledon.

Development of the Ovulate Strobilus and Young Ovule of Zamia Floridana

1. The young staminate and ovulate strobili can be distinguished by the difference in breadth, number of sporophylls, and number of meristematic points. 2. There is probably a single archesporial cell giving rise to a group of cells, one of which becomes the megaspore mother cell. 3. There are four potential megaspores, the lowest one becoming the embryo sac, whose development agrees with the accounts of other cycads in the main points. 4. The spongy tissue is an active, nutritive tissue, adding to its width by division of its cells as it is encroached upon by the embryo sac. 5. In its final degeneration, the cells of the spongy tissue nearest the embryo sac are first attacked, and the smaller cells outside them take their place, becoming large, swollen, and nutritive in function.

The Morphology of Phyllocladus alpinus

The microsporophyll has two abaxial sporangia and the microspores are shed on November 1 or before. Two prothallial cells are formed, the first of which is generally evanescent; sometimes both persist as free nuclei, the walls of both being evanescent. The mature microspore has usually four free nuclei, and occasionally five. The ovulate strobilus is borne on the phylloclad, and bears two to eight ovules. The ovule has two integuments; one thick and fleshy, the other (arillus) thin and leathery and persistent only at the base. They are free from the nucellus to its base, and contain no vascular strands. Microspores are found resting on the top of the nucellus on November 1, and occasionally pollen tubes and archegonia are formed at this date. Pollen tubes are very numerous and pass in a comparatively straight line through the nucellus to the archegonium. They smash the neck cells, if there are any, and empty their entire contents into the egg; the contents of one or more pollen tubes were found in an egg after the eight-nucleate stage of the proembryo. The body cell divides into two equal male cells just before discharge into the egg; and only one male cell functions. The archegonium is surrounded by a heavy jacket layer, consisting of multinucleate cells with large nuclei. Two neck cells are probably formed. No ventral cell or nucleus was found, but the material does not justify a definite statement as to its occurrence or not. The male cell is surrounded by a cytoplasmic sheath which, partly at least, surrounds the fusion nucleus. At least eight free nuclei are formed by the proembryo before cell walls are formed; and a long suspensor is developed.

The Ovule and Female Gametophyte of Dioon

1. Dioon occurs in abundance at Chavarrillo, Mexico. 2. It is probable that plants often reach an age of more than one thousand years. 3. The ovulate strobilus is more like the loose ovulate strobilus of Cycas than the compact ovulate strobili of the other genera. 4. The megasporophylls are more leaf-like than those of any other genus of cycads except Cycas. 5. The integument consists of three layers: an outer and an inner fleshy layer, with a stony layer between them. The integument is probably double in nature, the outer fleshy layer representing the outer integument. 6. Only a small portion of the nucellus is free from the integument. 7. One vascular bundle passes from the sporophyll toward each ovule. Before entering the ovule the bundle forks, one branch forming the continuously branching system of the inner fleshy layer of the integument, and the other forming the slightly branched system of the outer fleshy layer. 8. The megaspore membrane varies in thickness from 3-4. 5 μ in young ovules to 9-10 μ in mature seeds. 9. The number of archegonia varies from one to ten, with four and five as the most frequent numbers. The archegonium initial appears in October; the division into neck and central cell takes place almost immediately after; the mitosis which forms the ventral canal nucleus and egg nucleus takes place during the next May. 10. The central cell and egg during earlier stages receive food substances by the ordinary method of nutrition, but later receive food material through haustorial projections from the egg which are in direct contact with the cytoplasm of the jacket cells. 11. There are twelve chromosomes in the egg nucleus, which is the largest one yet known in plants.

Gametophytes and Embryo of Torreya Taxifolia

The staminate strobilus consists of a series of closely overlapping sterile bracts, in four vertical rows, completely enveloping the tip of the axis bearing numerous stamens. The large adaxial resin cavity that occurs in the stamen occupies the site of three abortive sporangia. The male gametophyte has no prothallial cell, and the male cells are very unequal, resembling those of Taxus. The pollen tube is exceedingly variable in the rate and direction of its advance through the nucellar cap, sometimes pushing in the embryo sac while it is in an early free-nucleate stage. The ovulate strobilus consists of four enveloping bracts and a single terminal ovule with two integuments. Extensive intercalary growth below the mother-cell forms the bulk of the mature ovule and seed. There is no organization of a special digestive layer around the mother-cell. The solitary archegonium initial appears as soon as walls are formed, is always at one side of the central axis of the gametophyte, and forms a two-celled neck. T...

The Embryogeny of Zamia

Previous articleNext article FreeThe Embryogeny of ZamiaJohn M. Coulter and Charles J. ChamberlainJohn M. Coulter Search for more articles by this author and Charles J. Chamberlain Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 35, Number 3Mar., 1903 Article DOIhttps://doi.org/10.1086/328334 Views: 163Total views on this site Citations: 11Citations are reported from Crossref Journal History This article was published in the Botanical Gazette (1876-1991), which is continued by International Journal of Plant Sciences (1992-present). PDF download Crossref reports the following articles citing this article:Roger Buvat Segmentation and First Edification of the Sporophyte, (Jan 1989): 8–104.https://doi.org/10.1007/978-3-642-73635-3_5Michel Monnier, Knut Norstog Developmental Aspects of Immature Zamia Embryos Cultured in vitro, Zeitschrift für Pflanzenphysiologie 113, no.22 (Jan 1984): 105–115.https://doi.org/10.1016/S0044-328X(84)80046-XR. N. Konar, Alok Moitra Ultrastructure, cyto- and histochemistry of female gametophyte of gymnosperms, Gamete Research 3, no.11 (Jan 1980): 67–97.https://doi.org/10.1002/mrd.1120030108George S. Bryan, Richard I. Evans CHROMATIN BEHAVIOR IN THE DEVELOPMENT AND MATURATION OF THE EGG NUCLEUS OF ZAMIA UMBROSA, American Journal of Botany 43, no.99 (Nov 1956): 640–646.https://doi.org/10.1002/j.1537-2197.1956.tb14427.xGeorge S. Bryan THE CELLULAR PROEMBRYO OF ZAMIA AND ITS CAP CELLS, American Journal of Botany 39, no.77 (Jul 1952): 433–443.https://doi.org/10.1002/j.1537-2197.1952.tb13051.x Marion A. Johnson Structure of the Shoot Apex in Zamia, Botanical Gazette 101, no.11 (Oct 2015): 189–203.https://doi.org/10.1086/334858A. Anstruther Lawson VI.—A Contribution to the Life-History of Bowenia, Transactions of the Royal Society of Edinburgh 54, no.22 (Jul 2012): 357–394.https://doi.org/10.1017/S0080456800027630 Paul J. Sedgwick Life History of Encephalartos, Botanical Gazette 77, no.33 (Sep 2015): 300–310.https://doi.org/10.1086/333317E. Hannig Über die Bedeutung der Periplasmodien, Flora oder Allgemeine Botanische Zeitung 102, no.44 (Apr 1911): 335–382.https://doi.org/10.1016/S0367-1615(17)32362-5 Charles J. Chamberlain Fertilization and Embryogeny in Dioon edule, Botanical Gazette 50, no.66 (Oct 2015): 415–429.https://doi.org/10.1086/330406 Otis W. Caldwell Microcycas Calocoma, Botanical Gazette 44, no.22 (Sep 2015): 118–141.https://doi.org/10.1086/329295