Gametophyte, female

Pistil Stigma (Female Gametophyte) of Seed-bearing Plants 14... 

PISTIL STIGMA (FEMALE GAMETOPHYTE) OF SEED-BEARING PLANTS... 

Stelly, D. M., Peloquin, S. J. (1986a). Diploid female gametophyte formation in 24-ehromosome potatoes genetie evidence for the prevalenee of the seeond meiotie division restitution mode. Canadian Journal of Genetics and Cytology, 28,101-108. 

Sporophyte producing seeds, the female gametophyte always parasitic in the megasporangium (ovule) during its entire... 

A Male and female gametophytes present, sporophyte represented by the zygote and the gonimoblasts produced from it.Order Nemalionales... 

B Male and female gametophytes alternating with sporophytes. 

A One prothallial cell female gametophyte entirely cellular at time of fertilization plant with only two permanent leaves. .Order Tumboales... 

B No prothallial cell female gametophyte coenocytic at micropylar end at the time of fertilization plants with many opposite... 

The embryo develops from a zygote formed by fusion of a sperm nucleus originating from the pollen and an egg cell. The fertilized egg is surrounded in the gynmosperms by a nutritive layer or endosperm which is haploid and is derived from the same game-tophyte tissue that produced the egg. In angiosperms two sperm nuclei form one of these fertilizes the egg, while the other fuses with two haploid polar nuclei derived from the female gametophyte. (The polar nuclei are formed by the same mitotic divisions that formed the egg.) From this develops a 3n triploid endosperm. 

The presence of spermatozoid-releasing and spermatozoid-attracting substances released from the eggs of marine brown algae was first suggested for the Fucus species in the first half of the twentieth century.14 In 1971, Muller et al 5 reported the isolation of ectocarpene (1) from fertile female gametophytes of the cosmopolitan... 

The Gametophyte generation of the White Pine begins with the development of the male and female gametophytes and terminates with the fertilization of the egg. 

Each archegonium consists of a much-reduced neck of four cells and an egg (ovum) which lies embedded in the prothallus which forms a narrow layer of cells around it called the jacket. The contents of the mature embryo-sac constitutes the female gametophyte. 

Before the pollen grain has been deposited upon the stigma and during its germination thereon, a series of events affecting both the pollen grain and the embryo sac occur which result in the ultimate formation of the male and female gametophytes. 

Maturation of the Embryo Sac and Formation of the Female Gametophyte.— The nucleus of the megaspore or embryo sac undergoes division until eight daughter-nuclei are produced which are separated into the following groups ... 

Fig. 97.—A, Immature angiospermous ovule B, same, after embryo-sac e.s). has matured to form the female gametophyte nucellus nuc) outer integument (0. int) inner integument (t. int) embryo sac e.s.) micropyle mic) chalaza ch) funiculus (/) synergids s) ovum (0) polar nuclei p) antipodals a) C, fertilized and matured angiospermous ovule (seed). Note that the nucellus nuc) has been pushed out by the encroachment of the embryo sac, in which endosperm has formed by the fusion of the two polar nuclei with the second sperm nucleus from the pollen tube which has later divided to form numerous nuclei scattered about in the protoplasm of the embryo sac and accumulated protoplasm and laid down walls, within which nourishment was stored embryo em) from fertilized ovum testa t) from outer integument tegmen te) from maturation of inner. integument micropyle mic) hilum or scar (h), after funiculus became detached.

Fig. 154.—Hair-cap moss (Polylrichum commune). A, male plant B, same, proliferating C, female plant, bearing sporogonium D, same g, gametophyte s, seta c, capsule 0, operculum a, calpytra E, top view of male plant. (Gager.),...

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